<?xml version="1.0" encoding="utf-8" ?> <!DOCTYPE erlref SYSTEM "erlref.dtd"> <erlref> <header> <copyright> <year>1997</year><year>2016</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. </legalnotice> <title>inet</title> <prepared>bjorn@erix.ericsson.se</prepared> <docno></docno> <date>1998-02-04</date> <rev>A</rev> </header> <module>inet</module> <modulesummary>Access to TCP/IP protocols.</modulesummary> <description> <p>This module provides access to TCP/IP protocols.</p> <p>See also <seealso marker="erts:inet_cfg">ERTS User's Guide: Inet Configuration</seealso> for more information about how to configure an Erlang runtime system for IP communication.</p> <p>The following two Kernel configuration parameters affect the behavior of all sockets opened on an Erlang node:</p> <list type="bulleted"> <item><p><c>inet_default_connect_options</c> can contain a list of default options used for all sockets returned when doing <c>connect</c>.</p></item> <item><p><c>inet_default_listen_options</c> can contain a list of default options used when issuing a <c>listen</c> call.</p></item> </list> <p>When <c>accept</c> is issued, the values of the listening socket options are inherited. No such application variable is therefore needed for <c>accept</c>.</p> <p>Using the Kernel configuration parameters above, one can set default options for all TCP sockets on a node, but use this with care. Options such as <c>{delay_send,true}</c> can be specified in this way. The following is an example of starting an Erlang node with all sockets using delayed send:</p> <pre> $ <input>erl -sname test -kernel \</input> <input>inet_default_connect_options '[{delay_send,true}]' \</input> <input>inet_default_listen_options '[{delay_send,true}]'</input></pre> <p>Notice that default option <c>{active, true}</c> cannot be changed, for internal reasons.</p> <p>Addresses as inputs to functions can be either a string or a tuple. For example, the IP address 150.236.20.73 can be passed to <c>gethostbyaddr/1</c>, either as string <c>"150.236.20.73"</c> or as tuple <c>{150, 236, 20, 73}</c>.</p> <p><em>IPv4 address examples:</em></p> <code type="none"> Address ip_address() ------- ------------ 127.0.0.1 {127,0,0,1} 192.168.42.2 {192,168,42,2}</code> <p><em>IPv6 address examples:</em></p> <code type="none"> Address ip_address() ------- ------------ ::1 {0,0,0,0,0,0,0,1} ::192.168.42.2 {0,0,0,0,0,0,(192 bsl 8) bor 168,(42 bsl 8) bor 2} FFFF::192.168.42.2 {16#FFFF,0,0,0,0,0,(192 bsl 8) bor 168,(42 bsl 8) bor 2} 3ffe:b80:1f8d:2:204:acff:fe17:bf38 {16#3ffe,16#b80,16#1f8d,16#2,16#204,16#acff,16#fe17,16#bf38} fe80::204:acff:fe17:bf38 {16#fe80,0,0,0,0,16#204,16#acff,16#fe17,16#bf38}</code> <p>Function <seealso marker="#parse_address/1"><c>parse_address/1</c></seealso> can be useful:</p> <pre> 1> <input>inet:parse_address("192.168.42.2").</input> {ok,{192,168,42,2}} 2> <input>inet:parse_address("FFFF::192.168.42.2").</input> {ok,{65535,0,0,0,0,0,49320,10754}}</pre> </description> <datatypes> <datatype> <name name="hostent"/> <desc> <p>The record is defined in the Kernel include file <c>"inet.hrl"</c>.</p> <p>Add the following directive to the module:</p> <code> -include_lib("kernel/include/inet.hrl").</code> </desc> </datatype> <datatype> <name name="hostname"/> </datatype> <datatype> <name name="ip_address"/> </datatype> <datatype> <name name="ip4_address"/> </datatype> <datatype> <name name="ip6_address"/> </datatype> <datatype> <name name="port_number"/> </datatype> <datatype> <name name="local_address"/> <desc> <p> This address family only works on Unix-like systems. </p> <p> <c><anno>File</anno></c> is normally a file pathname in a local filesystem. It is limited in length by the operating system, traditionally to 108 bytes. </p> <p> A <c>binary()</c> is passed as is to the operating system, but a <c>string()</c> is encoded according to the <seealso marker="file#native_name_encoding/0"> system filename encoding mode. </seealso> </p> <p> Other addresses are possible, for example Linux implements "Abstract Addresses". See the documentation for Unix Domain Sockets on your system, normally <c>unix</c> in manual section 7. </p> <p> In most API functions where you can use this address family the port number must be <c>0</c>. </p> </desc> </datatype> <datatype> <name name="socket_address"/> </datatype> <datatype> <name name="socket_getopt"/> </datatype> <datatype> <name name="socket_setopt"/> </datatype> <datatype> <name name="returned_non_ip_address"/> <desc> <p> Addresses besides <seealso marker="#type-ip_address"> <c>ip_address()</c> </seealso> ones that are returned from socket API functions. See in particular <seealso marker="#type-local_address"> <c>local_address()</c>. </seealso> The <c>unspec</c> family corresponds to AF_UNSPEC and can occur if the other side has no socket address. The <c>undefined</c> family can only occur in the unlikely event of an address family that the VM does not recognize. </p> </desc> </datatype> <datatype> <name name="posix"/> <desc> <p>An atom that is named from the POSIX error codes used in Unix, and in the runtime libraries of most C compilers. See section <seealso marker="#error_codes">POSIX Error Codes</seealso>.</p> </desc> </datatype> <datatype> <name>socket()</name> <desc> <p>See <seealso marker="gen_tcp#type-socket"><c>gen_tcp:type-socket</c></seealso> and <seealso marker="gen_udp#type-socket"><c>gen_udp:type-socket</c></seealso>. </p> </desc> </datatype> <datatype> <name name="address_family"/> </datatype> </datatypes> <funcs> <func> <name name="close" arity="1"/> <fsummary>Close a socket of any type.</fsummary> <desc> <p>Closes a socket of any type.</p> </desc> </func> <func> <name name="format_error" arity="1"/> <fsummary>Return a descriptive string for an error reason.</fsummary> <desc> <p>Returns a diagnostic error string. For possible POSIX values and corresponding strings, see section <seealso marker="#error_codes">POSIX Error Codes</seealso>.</p> </desc> </func> <func> <name name="get_rc" arity="0"/> <fsummary>Return a list of IP configuration parameters.</fsummary> <desc> <p>Returns the state of the <c>Inet</c> configuration database in form of a list of recorded configuration parameters. For more information, see <seealso marker="erts:inet_cfg">ERTS User's Guide: Inet Configuration</seealso>. Only parameters with other than default values are returned.</p> </desc> </func> <func> <name name="getaddr" arity="2"/> <fsummary>Return the IP address for a host.</fsummary> <desc> <p>Returns the IP address for <c><anno>Host</anno></c> as a tuple of integers. <c><anno>Host</anno></c> can be an IP address, a single hostname, or a fully qualified hostname.</p> </desc> </func> <func> <name name="getaddrs" arity="2"/> <fsummary>Return the IP addresses for a host.</fsummary> <desc> <p>Returns a list of all IP addresses for <c><anno>Host</anno></c>. <c><anno>Host</anno></c> can be an IP address, a single hostname, or a fully qualified hostname.</p> </desc> </func> <func> <name name="gethostbyaddr" arity="1"/> <fsummary>Return a hostent record for the host with the specified address.</fsummary> <desc> <p>Returns a <c>hostent</c> record for the host with the specified address.</p></desc> </func> <func> <name name="gethostbyname" arity="1"/> <fsummary>Return a hostent record for the host with the specified name. </fsummary> <desc> <p>Returns a <c>hostent</c> record for the host with the specified hostname.</p> <p>If resolver option <c>inet6</c> is <c>true</c>, an IPv6 address is looked up. If that fails, the IPv4 address is looked up and returned on IPv6-mapped IPv4 format.</p> </desc> </func> <func> <name name="gethostbyname" arity="2"/> <fsummary>Return a hostent record for the host with the specified name. </fsummary> <desc> <p>Returns a <c>hostent</c> record for the host with the specified name, restricted to the specified address family.</p> </desc> </func> <func> <name name="gethostname" arity="0"/> <fsummary>Return the local hostname.</fsummary> <desc> <p>Returns the local hostname. Never fails.</p> </desc> </func> <func> <name name="getifaddrs" arity="0"/> <fsummary>Return a list of interfaces and their addresses.</fsummary> <desc> <p>Returns a list of 2-tuples containing interface names and the interface addresses. <c><anno>Ifname</anno></c> is a Unicode string. <c><anno>Hwaddr</anno></c> is hardware dependent, for example, on Ethernet interfaces it is the 6-byte Ethernet address (MAC address (EUI-48 address)).</p> <p>The tuples <c>{addr,<anno>Addr</anno>}</c>, <c>{netmask,_}</c>, and <c>{broadaddr,_}</c> are repeated in the result list if the interface has multiple addresses. If you come across an interface with multiple <c>{flag,_}</c> or <c>{hwaddr,_}</c> tuples, you have a strange interface or possibly a bug in this function. The tuple <c>{flag,_}</c> is mandatory, all others are optional.</p> <p>Do not rely too much on the order of <c><anno>Flag</anno></c> atoms or <c><anno>Ifopt</anno></c> tuples. There are however some rules:</p> <list type="bulleted"> <item><p>Immediately after <c>{addr,_}</c> follows <c>{netmask,_}</c>.</p></item> <item><p>Immediately thereafter follows <c>{broadaddr,_}</c> if flag <c>broadcast</c> is <em>not</em> set and flag <c>pointtopoint</c> <em>is</em> set.</p></item> <item><p>Any <c>{netmask,_}</c>, <c>{broadaddr,_}</c>, or <c>{dstaddr,_}</c> tuples that follow an <c>{addr,_}</c> tuple concerns that address.</p></item> </list> <p>The tuple <c>{hwaddr,_}</c> is not returned on Solaris, as the hardware address historically belongs to the link layer and only the superuser can read such addresses.</p> <warning> <p>On Windows, the data is fetched from different OS API functions, so the <c><anno>Netmask</anno></c> and <c><anno>Broadaddr</anno></c> values can be calculated, just as some <c><anno>Flag</anno></c> values. Report flagrant bugs.</p> </warning> </desc> </func> <func> <name name="getopts" arity="2"/> <fsummary>Get one or more options for a socket.</fsummary> <desc> <p>Gets one or more options for a socket. For a list of available options, see <seealso marker="#setopts/2"><c>setopts/2</c></seealso>.</p> <p>The number of elements in the returned <c><anno>OptionValues</anno></c> list does not necessarily correspond to the number of options asked for. If the operating system fails to support an option, it is left out in the returned list. An error tuple is returned only when getting options for the socket is impossible (that is, the socket is closed or the buffer size in a raw request is too large). This behavior is kept for backward compatibility reasons.</p> <p>A raw option request <c>RawOptReq = {raw, Protocol, OptionNum, ValueSpec}</c> can be used to get information about socket options not (explicitly) supported by the emulator. The use of raw socket options makes the code non-portable, but allows the Erlang programmer to take advantage of unusual features present on the current platform.</p> <p><c>RawOptReq</c> consists of tag <c>raw</c> followed by the protocol level, the option number, and either a binary or the size, in bytes, of the buffer in which the option value is to be stored. A binary is to be used when the underlying <c>getsockopt</c> requires <em>input</em> in the argument field. In this case, the binary size is to correspond to the required buffer size of the return value. The supplied values in a <c>RawOptReq</c> correspond to the second, third, and fourth/fifth parameters to the <c>getsockopt</c> call in the C socket API. The value stored in the buffer is returned as a binary <c>ValueBin</c>, where all values are coded in the native endianess.</p> <p>Asking for and inspecting raw socket options require low-level information about the current operating system and TCP stack.</p> <p><em>Example:</em></p> <p>Consider a Linux machine where option <c>TCP_INFO</c> can be used to collect TCP statistics for a socket. Assume you are interested in field <c>tcpi_sacked</c> of <c>struct tcp_info</c> filled in when asking for <c>TCP_INFO</c>. To be able to access this information, you need to know the following:</p> <list type="bulleted"> <item>The numeric value of protocol level <c>IPPROTO_TCP</c></item> <item>The numeric value of option <c>TCP_INFO</c></item> <item>The size of <c>struct tcp_info</c></item> <item>The size and offset of the specific field</item> </list> <p>By inspecting the headers or writing a small C program, it is found that <c>IPPROTO_TCP</c> is 6, <c>TCP_INFO</c> is 11, the structure size is 92 (bytes), the offset of <c>tcpi_sacked</c> is 28 bytes, and the value is a 32-bit integer. The following code can be used to retrieve the value:</p> <code type="none"><![CDATA[ get_tcpi_sacked(Sock) -> {ok,[{raw,_,_,Info}]} = inet:getopts(Sock,[{raw,6,11,92}]), <<_:28/binary,TcpiSacked:32/native,_/binary>> = Info, TcpiSacked.]]></code> <p>Preferably, you would check the machine type, the operating system, and the Kernel version before executing anything similar to this code.</p> </desc> </func> <func> <name name="getstat" arity="1"/> <name name="getstat" arity="2"/> <fsummary>Get one or more statistic options for a socket.</fsummary> <type name="stat_option"/> <desc> <p>Gets one or more statistic options for a socket.</p> <p><c>getstat(<anno>Socket</anno>)</c> is equivalent to <c>getstat(<anno>Socket</anno>, [recv_avg, recv_cnt, recv_dvi, recv_max, recv_oct, send_avg, send_cnt, send_dvi, send_max, send_oct])</c>.</p> <p>The following options are available:</p> <taglist> <tag><c>recv_avg</c></tag> <item> <p>Average size of packets, in bytes, received by the socket.</p> </item> <tag><c>recv_cnt</c></tag> <item> <p>Number of packets received by the socket.</p> </item> <tag><c>recv_dvi</c></tag> <item> <p>Average packet size deviation, in bytes, received by the socket.</p> </item> <tag><c>recv_max</c></tag> <item> <p>Size of the largest packet, in bytes, received by the socket.</p> </item> <tag><c>recv_oct</c></tag> <item> <p>Number of bytes received by the socket.</p> </item> <tag><c>send_avg</c></tag> <item> <p>Average size of packets, in bytes, sent from the socket.</p> </item> <tag><c>send_cnt</c></tag> <item> <p>Number of packets sent from the socket.</p> </item> <tag><c>send_dvi</c></tag> <item> <p>Average packet size deviation, in bytes, sent from the socket.</p> </item> <tag><c>send_max</c></tag> <item> <p>Size of the largest packet, in bytes, sent from the socket.</p> </item> <tag><c>send_oct</c></tag> <item> <p>Number of bytes sent from the socket.</p> </item> </taglist> </desc> </func> <func> <name name="ntoa" arity="1" /> <fsummary>Convert IPv6/IPV4 address to ASCII.</fsummary> <desc> <p>Parses an <seealso marker="#type-ip_address"><c>ip_address()</c></seealso> and returns an IPv4 or IPv6 address string.</p> </desc> </func> <func> <name name="parse_address" arity="1" /> <fsummary>Parse an IPv4 or IPv6 address.</fsummary> <desc> <p>Parses an IPv4 or IPv6 address string and returns an <seealso marker="#type-ip4_address"><c>ip4_address()</c></seealso> or <seealso marker="#type-ip6_address"><c>ip6_address()</c></seealso>. Accepts a shortened IPv4 address string.</p> </desc> </func> <func> <name name="parse_ipv4_address" arity="1" /> <fsummary>Parse an IPv4 address.</fsummary> <desc> <p>Parses an IPv4 address string and returns an <seealso marker="#type-ip4_address"><c>ip4_address()</c></seealso>. Accepts a shortened IPv4 address string.</p> </desc> </func> <func> <name name="parse_ipv4strict_address" arity="1" /> <fsummary>Parse an IPv4 address strict.</fsummary> <desc> <p>Parses an IPv4 address string containing four fields, that is, <em>not</em> shortened, and returns an <seealso marker="#type-ip4_address"><c>ip4_address()</c></seealso>. </p> </desc> </func> <func> <name name="parse_ipv6_address" arity="1" /> <fsummary>Parse an IPv6 address.</fsummary> <desc> <p>Parses an IPv6 address string and returns an <seealso marker="#type-ip6_address"><c>ip6_address()</c></seealso>. If an IPv4 address string is specified, an IPv4-mapped IPv6 address is returned.</p> </desc> </func> <func> <name name="parse_ipv6strict_address" arity="1" /> <fsummary>Parse an IPv6 address strict.</fsummary> <desc> <p>Parses an IPv6 address string and returns an <seealso marker="#type-ip6_address"><c>ip6_address()</c></seealso>. Does <em>not</em> accept IPv4 addresses.</p> </desc> </func> <func> <name name="parse_strict_address" arity="1" /> <fsummary>Parse an IPv4 or IPv6 address strict.</fsummary> <desc> <p>Parses an IPv4 or IPv6 address string and returns an <seealso marker="#type-ip4_address"><c>ip4_address()</c></seealso> or <seealso marker="#type-ip6_address"><c>ip6_address()</c></seealso>. Does <em>not</em> accept a shortened IPv4 address string.</p> </desc> </func> <func> <name name="peername" arity="1"/> <fsummary>Return the address and port for the other end of a connection. </fsummary> <desc> <p>Returns the address and port for the other end of a connection.</p> <p>Notice that for SCTP sockets, this function returns only one of the peer addresses of the socket. Function <seealso marker="#peernames/1"><c>peernames/1,2</c></seealso> returns all.</p> </desc> </func> <func> <name name="peernames" arity="1"/> <fsummary>Return all address/port numbers for the other end of a connection.</fsummary> <desc> <p>Equivalent to <seealso marker="#peernames/2"><c>peernames(<anno>Socket</anno>, 0)</c></seealso>. </p> <p>Notice that the behavior of this function for an SCTP one-to-many style socket is not defined by the <url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">SCTP Sockets API Extensions</url>.</p> </desc> </func> <func> <name name="peernames" arity="2"/> <fsummary>Return all address/port numbers for the other end of a connection.</fsummary> <desc> <p>Returns a list of all address/port number pairs for the other end of an association <c><anno>Assoc</anno></c> of a socket.</p> <p>This function can return multiple addresses for multihomed sockets, such as SCTP sockets. For other sockets it returns a one-element list.</p> <p>Notice that parameter <c><anno>Assoc</anno></c> is by the <url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">SCTP Sockets API Extensions</url> defined to be ignored for one-to-one style sockets. What the special value <c>0</c> means, hence its behavior for one-to-many style sockets, is unfortunately undefined.</p> </desc> </func> <func> <name name="port" arity="1"/> <fsummary>Return the local port number for a socket.</fsummary> <desc> <p>Returns the local port number for a socket.</p> </desc> </func> <func> <name name="setopts" arity="2"/> <fsummary>Set one or more options for a socket.</fsummary> <desc> <p>Sets one or more options for a socket.</p> <p>The following options are available:</p> <taglist> <tag><c>{active, true | false | once | N}</c></tag> <item> <p>If the value is <c>true</c>, which is the default, everything received from the socket is sent as messages to the receiving process.</p> <p>If the value is <c>false</c> (passive mode), the process must explicitly receive incoming data by calling <seealso marker="gen_tcp#recv/2"><c>gen_tcp:recv/2,3</c></seealso>, <seealso marker="gen_udp#recv/2"><c>gen_udp:recv/2,3</c></seealso>, or <seealso marker="gen_sctp#recv/1"><c>gen_sctp:recv/1,2</c></seealso> (depending on the type of socket).</p> <p>If the value is <c>once</c> (<c>{active, once}</c>), <em>one</em> data message from the socket is sent to the process. To receive one more message, <c>setopts/2</c> must be called again with option <c>{active, once}</c>.</p> <p>If the value is an integer <c>N</c> in the range -32768 to 32767 (inclusive), the value is added to the socket's count of data messages sent to the controlling process. A socket's default message count is <c>0</c>. If a negative value is specified, and its magnitude is equal to or greater than the socket's current message count, the socket's message count is set to <c>0</c>. Once the socket's message count reaches <c>0</c>, either because of sending received data messages to the process or by being explicitly set, the process is then notified by a special message, specific to the type of socket, that the socket has entered passive mode. Once the socket enters passive mode, to receive more messages <c>setopts/2</c> must be called again to set the socket back into an active mode.</p> <p>When using <c>{active, once}</c> or <c>{active, N}</c>, the socket changes behavior automatically when data is received. This can be confusing in combination with connection-oriented sockets (that is, <c>gen_tcp</c>), as a socket with <c>{active, false}</c> behavior reports closing differently than a socket with <c>{active, true}</c> behavior. To simplify programming, a socket where the peer closed, and this is detected while in <c>{active, false}</c> mode, still generates message <c>{tcp_closed,Socket}</c> when set to <c>{active, once}</c>, <c>{active, true}</c>, or <c>{active, N}</c> mode. It is therefore safe to assume that message <c>{tcp_closed,Socket}</c>, possibly followed by socket port termination (depending on option <c>exit_on_close</c>) eventually appears when a socket changes back and forth between <c>{active, true}</c> and <c>{active, false}</c> mode. However, <em>when</em> peer closing is detected it is all up to the underlying TCP/IP stack and protocol.</p> <p>Notice that <c>{active, true}</c> mode provides no flow control; a fast sender can easily overflow the receiver with incoming messages. The same is true for <c>{active, N}</c> mode, while the message count is greater than zero.</p> <p>Use active mode only if your high-level protocol provides its own flow control (for example, acknowledging received messages) or the amount of data exchanged is small. <c>{active, false}</c> mode, use of the <c>{active, once}</c> mode, or <c>{active, N}</c> mode with values of <c>N</c> appropriate for the application provides flow control. The other side cannot send faster than the receiver can read.</p> </item> <tag><c>{broadcast, Boolean}</c> (UDP sockets)</tag> <item> <p>Enables/disables permission to send broadcasts.</p> <marker id="option-buffer"></marker> </item> <tag><c>{buffer, Size}</c></tag> <item> <p>The size of the user-level software buffer used by the driver. Not to be confused with options <c>sndbuf</c> and <c>recbuf</c>, which correspond to the Kernel socket buffers. It is recommended to have <c>val(buffer) >= max(val(sndbuf),val(recbuf))</c> to avoid performance issues because of unnecessary copying. <c>val(buffer)</c> is automatically set to the above maximum when values <c>sndbuf</c> or <c>recbuf</c> are set. However, as the sizes set for <c>sndbuf</c> and <c>recbuf</c> usually become larger, you are encouraged to use <seealso marker="#getopts/2"><c>getopts/2</c></seealso> to analyze the behavior of your operating system.</p> </item> <tag><c>{delay_send, Boolean}</c></tag> <item> <p>Normally, when an Erlang process sends to a socket, the driver tries to send the data immediately. If that fails, the driver uses any means available to queue up the message to be sent whenever the operating system says it can handle it. Setting <c>{delay_send, true}</c> makes <em>all</em> messages queue up. The messages sent to the network are then larger but fewer. The option affects the scheduling of send requests versus Erlang processes instead of changing any real property of the socket. The option is implementation-specific. Defaults to <c>false</c>.</p> </item> <tag><c>{deliver, port | term}</c></tag> <item> <p>When <c>{active, true}</c>, data is delivered on the form <c>port</c> : <c>{S, {data, [H1,..Hsz | Data]}}</c> or <c>term</c> : <c>{tcp, S, [H1..Hsz | Data]}</c>.</p> </item> <tag><c>{dontroute, Boolean}</c></tag> <item> <p>Enables/disables routing bypass for outgoing messages.</p> </item> <tag><c>{exit_on_close, Boolean}</c></tag> <item> <p>This option is set to <c>true</c> by default.</p> <p>The only reason to set it to <c>false</c> is if you want to continue sending data to the socket after a close is detected, for example, if the peer uses <seealso marker="gen_tcp#shutdown/2"><c>gen_tcp:shutdown/2</c></seealso> to shut down the write side.</p> </item> <tag><c>{header, Size}</c></tag> <item> <p>This option is only meaningful if option <c>binary</c> was specified when the socket was created. If option <c>header</c> is specified, the first <c>Size</c> number bytes of data received from the socket are elements of a list, and the remaining data is a binary specified as the tail of the same list. For example, if <c>Size == 2</c>, the data received matches <c>[Byte1,Byte2|Binary]</c>.</p> </item> <tag><c>{high_msgq_watermark, Size}</c></tag> <item> <p>The socket message queue is set to a busy state when the amount of data on the message queue reaches this limit. Notice that this limit only concerns data that has not yet reached the ERTS internal socket implementation. Defaults to 8 kB.</p> <p>Senders of data to the socket are suspended if either the socket message queue is busy or the socket itself is busy.</p> <p>For more information, see options <c>low_msgq_watermark</c>, <c>high_watermark</c>, and <c>low_watermark</c>.</p> <p>Notice that distribution sockets disable the use of <c>high_msgq_watermark</c> and <c>low_msgq_watermark</c>. Instead use the <seealso marker="erts:erlang#system_info_dist_buf_busy_limit">distribution buffer busy limit</seealso>, which is a similar feature.</p> </item> <tag><c>{high_watermark, Size}</c> (TCP/IP sockets)</tag> <item> <p>The socket is set to a busy state when the amount of data queued internally by the ERTS socket implementation reaches this limit. Defaults to 8 kB.</p> <p>Senders of data to the socket are suspended if either the socket message queue is busy or the socket itself is busy.</p> <p>For more information, see options <c>low_watermark</c>, <c>high_msgq_watermark</c>, and <c>low_msqg_watermark</c>.</p> </item> <tag><c>{ipv6_v6only, Boolean}</c></tag> <item> <p>Restricts the socket to use only IPv6, prohibiting any IPv4 connections. This is only applicable for IPv6 sockets (option <c>inet6</c>).</p> <p>On most platforms this option must be set on the socket before associating it to an address. It is therefore only reasonable to specify it when creating the socket and not to use it when calling function (<seealso marker="#setopts/2"><c>setopts/2</c></seealso>) containing this description.</p> <p>The behavior of a socket with this option set to <c>true</c> is the only portable one. The original idea when IPv6 was new of using IPv6 for all traffic is now not recommended by FreeBSD (you can use <c>{ipv6_v6only,false}</c> to override the recommended system default value), forbidden by OpenBSD (the supported GENERIC kernel), and impossible on Windows (which has separate IPv4 and IPv6 protocol stacks). Most Linux distros still have a system default value of <c>false</c>. This policy shift among operating systems to separate IPv6 from IPv4 traffic has evolved, as it gradually proved hard and complicated to get a dual stack implementation correct and secure.</p> <p>On some platforms, the only allowed value for this option is <c>true</c>, for example, OpenBSD and Windows. Trying to set this option to <c>false</c>, when creating the socket, fails in this case.</p> <p>Setting this option on platforms where it does not exist is ignored. Getting this option with <seealso marker="#getopts/2"><c>getopts/2</c></seealso> returns no value, that is, the returned list does not contain an <c>{ipv6_v6only,_}</c> tuple. On Windows, the option does not exist, but it is emulated as a read-only option with value <c>true</c>.</p> <p>Therefore, setting this option to <c>true</c> when creating a socket never fails, except possibly on a platform where you have customized the kernel to only allow <c>false</c>, which can be doable (but awkward) on, for example, OpenBSD.</p> <p>If you read back the option value using <seealso marker="#getopts/2"><c>getopts/2</c></seealso> and get no value, the option does not exist in the host operating system. The behavior of both an IPv6 and an IPv4 socket listening on the same port, and for an IPv6 socket getting IPv4 traffic is then no longer predictable.</p> </item> <tag><c>{keepalive, Boolean}</c>(TCP/IP sockets)</tag> <item> <p>Enables/disables periodic transmission on a connected socket when no other data is exchanged. If the other end does not respond, the connection is considered broken and an error message is sent to the controlling process. Defaults to <c>disabled</c>.</p> <marker id="option-linger"></marker> </item> <tag><c>{linger, {true|false, Seconds}}</c></tag> <item> <p>Determines the time-out, in seconds, for flushing unsent data in the <c>close/1</c> socket call. If the first component of the value tuple is <c>false</c>, the second is ignored. This means that <c>close/1</c> returns immediately, not waiting for data to be flushed. Otherwise, the second component is the flushing time-out, in seconds.</p> </item> <tag><c>{low_msgq_watermark, Size}</c></tag> <item> <p>If the socket message queue is in a busy state, the socket message queue is set in a not busy state when the amount of data queued in the message queue falls below this limit. Notice that this limit only concerns data that has not yet reached the ERTS internal socket implementation. Defaults to 4 kB.</p> <p>Senders that are suspended because of either a busy message queue or a busy socket are resumed when the socket message queue and the socket are not busy.</p> <p>For more information, see options <c>high_msgq_watermark</c>, <c>high_watermark</c>, and <c>low_watermark</c>.</p> <p>Notice that distribution sockets disable the use of <c>high_msgq_watermark</c> and <c>low_msgq_watermark</c>. Instead they use the <seealso marker="erts:erlang#system_info_dist_buf_busy_limit">distribution buffer busy limit</seealso>, which is a similar feature.</p> </item> <tag><c>{low_watermark, Size}</c> (TCP/IP sockets)</tag> <item> <p>If the socket is in a busy state, the socket is set in a not busy state when the amount of data queued internally by the ERTS socket implementation falls below this limit. Defaults to 4 kB.</p> <p>Senders that are suspended because of a busy message queue or a busy socket are resumed when the socket message queue and the socket are not busy.</p> <p>For more information, see options <c>high_watermark</c>, <c>high_msgq_watermark</c>, and <c>low_msgq_watermark</c>.</p> </item> <tag><c>{mode, Mode :: binary | list}</c></tag> <item> <p>Received <c>Packet</c> is delivered as defined by <c>Mode</c>. </p> </item> <tag><c>{netns, Namespace :: file:filename_all()}</c></tag> <item> <p>Sets a network namespace for the socket. Parameter <c>Namespace</c> is a filename defining the namespace, for example, <c>"/var/run/netns/example"</c>, typically created by command <c>ip netns add example</c>. This option must be used in a function call that creates a socket, that is, <seealso marker="gen_tcp#connect/3"><c>gen_tcp:connect/3,4</c></seealso>, <seealso marker="gen_tcp#listen/2"><c>gen_tcp:listen/2</c></seealso>, <seealso marker="gen_udp#open/1"><c>gen_udp:open/1,2</c></seealso>, or <seealso marker="gen_sctp#open/0"><c>gen_sctp:open/0,1,2</c></seealso>.</p> <p>This option uses the Linux-specific syscall <c>setns()</c>, such as in Linux kernel 3.0 or later, and therefore only exists when the runtime system is compiled for such an operating system.</p> <p>The virtual machine also needs elevated privileges, either running as superuser or (for Linux) having capability <c>CAP_SYS_ADMIN</c> according to the documentation for <c>setns(2)</c>. However, during testing also <c>CAP_SYS_PTRACE</c> and <c>CAP_DAC_READ_SEARCH</c> have proven to be necessary.</p> <p><em>Example:</em></p> <code> setcap cap_sys_admin,cap_sys_ptrace,cap_dac_read_search+epi beam.smp</code> <p>Notice that the filesystem containing the virtual machine executable (<c>beam.smp</c> in the example) must be local, mounted without flag <c>nosetuid</c>, support extended attributes, and the kernel must support file capabilities. All this runs out of the box on at least Ubuntu 12.04 LTS, except that SCTP sockets appear to not support network namespaces.</p> <p><c>Namespace</c> is a filename and is encoded and decoded as discussed in module <seealso marker="file">file</seealso>, with the following exceptions:</p> <list type="bulleted"> <item><p>Emulator flag <c>+fnu</c> is ignored.</p></item> <item><p><seealso marker="#getopts/2"><c>getopts/2</c></seealso> for this option returns a binary for the filename if the stored filename cannot be decoded. This is only to occur if you set the option using a binary that cannot be decoded with the emulator's filename encoding: <seealso marker="file#native_name_encoding/0"><c>file:native_name_encoding/0</c></seealso>.</p></item> </list> </item> <tag><c>list</c></tag> <item> <p>Received <c>Packet</c> is delivered as a list.</p> </item> <tag><c>binary</c></tag> <item> <p>Received <c>Packet</c> is delivered as a binary.</p> </item> <tag><c>{nodelay, Boolean}</c>(TCP/IP sockets)</tag> <item> <p>If <c>Boolean == true</c>, option <c>TCP_NODELAY</c> is turned on for the socket, which means that also small amounts of data are sent immediately.</p> </item> <tag><c>{packet, PacketType}</c>(TCP/IP sockets)</tag> <item> <p>Defines the type of packets to use for a socket. Possible values:</p> <taglist> <tag><c>raw | 0</c></tag> <item> <p>No packaging is done.</p> </item> <tag><c>1 | 2 | 4</c></tag> <item> <p>Packets consist of a header specifying the number of bytes in the packet, followed by that number of bytes. The header length can be one, two, or four bytes, and containing an unsigned integer in big-endian byte order. Each send operation generates the header, and the header is stripped off on each receive operation.</p> <p>The 4-byte header is limited to 2Gb.</p> </item> <tag><c>asn1 | cdr | sunrm | fcgi | tpkt | line</c></tag> <item> <p>These packet types only have effect on receiving. When sending a packet, it is the responsibility of the application to supply a correct header. On receiving, however, one message is sent to the controlling process for each complete packet received, and, similarly, each call to <c>gen_tcp:recv/2,3</c> returns one complete packet. The header is <em>not</em> stripped off.</p> <p>The meanings of the packet types are as follows:</p> <list type="bulleted"> <item><c>asn1</c> - ASN.1 BER</item> <item><c>sunrm</c> - Sun's RPC encoding</item> <item><c>cdr</c> - CORBA (GIOP 1.1)</item> <item><c>fcgi</c> - Fast CGI</item> <item><c>tpkt</c> - TPKT format [RFC1006]</item> <item><c>line</c> - Line mode, a packet is a line-terminated with newline, lines longer than the receive buffer are truncated</item> </list> </item> <tag><c>http | http_bin</c></tag> <item> <p>The Hypertext Transfer Protocol. The packets are returned with the format according to <c>HttpPacket</c> described in <seealso marker="erts:erlang#decode_packet/3"> <c>erlang:decode_packet/3</c></seealso> in ERTS. A socket in passive mode returns <c>{ok, HttpPacket}</c> from <c>gen_tcp:recv</c> while an active socket sends messages like <c>{http, Socket, HttpPacket}</c>.</p> </item> <tag><c>httph | httph_bin</c></tag> <item> <p>These two types are often not needed, as the socket automatically switches from <c>http</c>/<c>http_bin</c> to <c>httph</c>/<c>httph_bin</c> internally after the first line is read. However, there can be occasions when they are useful, such as parsing trailers from chunked encoding.</p> </item> </taglist> </item> <tag><c>{packet_size, Integer}</c>(TCP/IP sockets)</tag> <item> <p>Sets the maximum allowed length of the packet body. If the packet header indicates that the length of the packet is longer than the maximum allowed length, the packet is considered invalid. The same occurs if the packet header is too large for the socket receive buffer.</p> <p>For line-oriented protocols (<c>line</c>, <c>http*</c>), option <c>packet_size</c> also guarantees that lines up to the indicated length are accepted and not considered invalid because of internal buffer limitations.</p> </item> <tag><c>{line_delimiter, Char}</c>(TCP/IP sockets)</tag> <item> <p>Sets the line delimiting character for line-oriented protocols (<c>line</c>). Defaults to <c>$\n</c>.</p> </item> <tag><c>{raw, Protocol, OptionNum, ValueBin}</c></tag> <item> <p>See below.</p> </item> <tag><c>{read_packets, Integer}</c>(UDP sockets)</tag> <item> <p>Sets the maximum number of UDP packets to read without intervention from the socket when data is available. When this many packets have been read and delivered to the destination process, new packets are not read until a new notification of available data has arrived. Defaults to <c>5</c>. If this parameter is set too high, the system can become unresponsive because of UDP packet flooding.</p> </item> <tag><c>{recbuf, Size}</c></tag> <item> <p>The minimum size of the receive buffer to use for the socket. You are encouraged to use <seealso marker="#getopts/2"><c>getopts/2</c></seealso> to retrieve the size set by your operating system.</p> </item> <tag><c>{reuseaddr, Boolean}</c></tag> <item> <p>Allows or disallows local reuse of port numbers. By default, reuse is disallowed.</p> </item> <tag><c>{send_timeout, Integer}</c></tag> <item> <p>Only allowed for connection-oriented sockets.</p> <p>Specifies a longest time to wait for a send operation to be accepted by the underlying TCP stack. When the limit is exceeded, the send operation returns <c>{error,timeout}</c>. How much of a packet that got sent is unknown; the socket is therefore to be closed whenever a time-out has occurred (see <c>send_timeout_close</c> below). Defaults to <c>infinity</c>.</p> </item> <tag><c>{send_timeout_close, Boolean}</c></tag> <item> <p>Only allowed for connection-oriented sockets.</p> <p>Used together with <c>send_timeout</c> to specify whether the socket is to be automatically closed when the send operation returns <c>{error,timeout}</c>. The recommended setting is <c>true</c>, which automatically closes the socket. Defaults to <c>false</c> because of backward compatibility.</p> <marker id="option-sndbuf"></marker> </item> <tag><c>{show_econnreset, Boolean}</c>(TCP/IP sockets)</tag> <item> <p>When this option is set to <c>false</c>, which is default, an RST received from the TCP peer is treated as a normal close (as though an FIN was sent). A caller to <seealso marker="gen_tcp#recv/2"><c>gen_tcp:recv/2</c></seealso> gets <c>{error, closed}</c>. In active mode, the controlling process receives a <c>{tcp_close, Socket}</c> message, indicating that the peer has closed the connection.</p> <p>Setting this option to <c>true</c> allows you to distinguish between a connection that was closed normally, and one that was aborted (intentionally or unintentionally) by the TCP peer. A call to <seealso marker="gen_tcp#recv/2"><c>gen_tcp:recv/2</c></seealso> returns <c>{error, econnreset}</c>. In active mode, the controlling process receives a <c>{tcp_error, Socket, econnreset}</c> message before the usual <c>{tcp_closed, Socket}</c>, as is the case for any other socket error. Calls to <seealso marker="gen_tcp#send/2"><c>gen_tcp:send/2</c></seealso> also returns <c>{error, econnreset}</c> when it is detected that a TCP peer has sent an RST.</p> <p>A connected socket returned from <seealso marker="gen_tcp#accept/1"><c>gen_tcp:accept/1</c></seealso> inherits the <c>show_econnreset</c> setting from the listening socket.</p> <marker id="option-show_econnreset"></marker> </item> <tag><c>{sndbuf, Size}</c></tag> <item> <p>The minimum size of the send buffer to use for the socket. You are encouraged to use <seealso marker="#getopts/2"><c>getopts/2</c></seealso>, to retrieve the size set by your operating system.</p> </item> <tag><c>{priority, Integer}</c></tag> <item> <p>Sets the <c>SO_PRIORITY</c> socket level option on platforms where this is implemented. The behavior and allowed range varies between different systems. The option is ignored on platforms where it is not implemented. Use with caution.</p> </item> <tag><c>{tos, Integer}</c></tag> <item> <p>Sets <c>IP_TOS IP</c> level options on platforms where this is implemented. The behavior and allowed range varies between different systems. The option is ignored on platforms where it is not implemented. Use with caution.</p> </item> <tag><c>{tclass, Integer}</c></tag> <item> <p> Sets <c>IPV6_TCLASS IP</c> level options on platforms where this is implemented. The behavior and allowed range varies between different systems. The option is ignored on platforms where it is not implemented. Use with caution.</p> </item> </taglist> <p>In addition to these options, <em>raw</em> option specifications can be used. The raw options are specified as a tuple of arity four, beginning with tag <c>raw</c>, followed by the protocol level, the option number, and the option value specified as a binary. This corresponds to the second, third, and fourth arguments to the <c>setsockopt</c> call in the C socket API. The option value must be coded in the native endianess of the platform and, if a structure is required, must follow the structure alignment conventions on the specific platform.</p> <p>Using raw socket options requires detailed knowledge about the current operating system and TCP stack.</p> <p><em>Example:</em></p> <p>This example concerns the use of raw options. Consider a Linux system where you want to set option <c>TCP_LINGER2</c> on protocol level <c>IPPROTO_TCP</c> in the stack. You know that on this particular system it defaults to 60 (seconds), but you want to lower it to 30 for a particular socket. Option <c>TCP_LINGER2</c> is not explicitly supported by <c>inet</c>, but you know that the protocol level translates to number 6, the option number to number 8, and the value is to be specified as a 32-bit integer. You can use this code line to set the option for the socket named <c>Sock</c>:</p> <code type="none"><![CDATA[ inet:setopts(Sock,[{raw,6,8,<<30:32/native>>}]),]]></code> <p>As many options are silently discarded by the stack if they are specified out of range; it can be a good idea to check that a raw option is accepted. The following code places the value in variable <c>TcpLinger2:</c></p> <code type="none"><![CDATA[ {ok,[{raw,6,8,<<TcpLinger2:32/native>>}]}=inet:getopts(Sock,[{raw,6,8,4}]),]]></code> <p>Code such as these examples is inherently non-portable, even different versions of the same OS on the same platform can respond differently to this kind of option manipulation. Use with care.</p> <p>Notice that the default options for TCP/IP sockets can be changed with the Kernel configuration parameters mentioned in the beginning of this manual page.</p> </desc> </func> <func> <name name="sockname" arity="1"/> <fsummary>Return the local address and port number for a socket. </fsummary> <desc> <p>Returns the local address and port number for a socket.</p> <p>Notice that for SCTP sockets this function returns only one of the socket addresses. Function <seealso marker="#socknames/1"><c>socknames/1,2</c></seealso> returns all.</p> </desc> </func> <func> <name name="socknames" arity="1"/> <fsummary>Return all local address/port numbers for a socket.</fsummary> <desc> <p>Equivalent to <seealso marker="#socknames/2"><c>socknames(<anno>Socket</anno>, 0)</c></seealso>. </p> </desc> </func> <func> <name name="socknames" arity="2"/> <fsummary>Return all local address/port numbers for a socket.</fsummary> <desc> <p>Returns a list of all local address/port number pairs for a socket for the specified association <c><anno>Assoc</anno></c>.</p> <p>This function can return multiple addresses for multihomed sockets, such as SCTP sockets. For other sockets it returns a one-element list.</p> <p>Notice that parameter <c><anno>Assoc</anno></c> is by the <url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">SCTP Sockets API Extensions</url> defined to be ignored for one-to-one style sockets. For one-to-many style sockets, the special value <c>0</c> is defined to mean that the returned addresses must be without any particular association. How different SCTP implementations interprets this varies somewhat. </p> </desc> </func> </funcs> <section> <marker id="error_codes"></marker> <title>POSIX Error Codes</title> <list type="bulleted"> <item><c>e2big</c> - Too long argument list</item> <item><c>eacces</c> - Permission denied</item> <item><c>eaddrinuse</c> - Address already in use</item> <item><c>eaddrnotavail</c> - Cannot assign requested address</item> <item><c>eadv</c> - Advertise error</item> <item><c>eafnosupport</c> - Address family not supported by protocol family</item> <item><c>eagain</c> - Resource temporarily unavailable</item> <item><c>ealign</c> - EALIGN</item> <item><c>ealready</c> - Operation already in progress</item> <item><c>ebade</c> - Bad exchange descriptor</item> <item><c>ebadf</c> - Bad file number</item> <item><c>ebadfd</c> - File descriptor in bad state</item> <item><c>ebadmsg</c> - Not a data message</item> <item><c>ebadr</c> - Bad request descriptor</item> <item><c>ebadrpc</c> - Bad RPC structure</item> <item><c>ebadrqc</c> - Bad request code</item> <item><c>ebadslt</c> - Invalid slot</item> <item><c>ebfont</c> - Bad font file format</item> <item><c>ebusy</c> - File busy</item> <item><c>echild</c> - No children</item> <item><c>echrng</c> - Channel number out of range</item> <item><c>ecomm</c> - Communication error on send</item> <item><c>econnaborted</c> - Software caused connection abort</item> <item><c>econnrefused</c> - Connection refused</item> <item><c>econnreset</c> - Connection reset by peer</item> <item><c>edeadlk</c> - Resource deadlock avoided</item> <item><c>edeadlock</c> - Resource deadlock avoided</item> <item><c>edestaddrreq</c> - Destination address required</item> <item><c>edirty</c> - Mounting a dirty fs without force</item> <item><c>edom</c> - Math argument out of range</item> <item><c>edotdot</c> - Cross mount point</item> <item><c>edquot</c> - Disk quota exceeded</item> <item><c>eduppkg</c> - Duplicate package name</item> <item><c>eexist</c> - File already exists</item> <item><c>efault</c> - Bad address in system call argument</item> <item><c>efbig</c> - File too large</item> <item><c>ehostdown</c> - Host is down</item> <item><c>ehostunreach</c> - Host is unreachable</item> <item><c>eidrm</c> - Identifier removed</item> <item><c>einit</c> - Initialization error</item> <item><c>einprogress</c> - Operation now in progress</item> <item><c>eintr</c> - Interrupted system call</item> <item><c>einval</c> - Invalid argument</item> <item><c>eio</c> - I/O error</item> <item><c>eisconn</c> - Socket is already connected</item> <item><c>eisdir</c> - Illegal operation on a directory</item> <item><c>eisnam</c> - Is a named file</item> <item><c>el2hlt</c> - Level 2 halted</item> <item><c>el2nsync</c> - Level 2 not synchronized</item> <item><c>el3hlt</c> - Level 3 halted</item> <item><c>el3rst</c> - Level 3 reset</item> <item><c>elbin</c> - ELBIN</item> <item><c>elibacc</c> - Cannot access a needed shared library</item> <item><c>elibbad</c> - Accessing a corrupted shared library</item> <item><c>elibexec</c> - Cannot exec a shared library directly</item> <item><c>elibmax</c> - Attempting to link in more shared libraries than system limit</item> <item><c>elibscn</c> - <c>.lib</c> section in <c>a.out</c> corrupted</item> <item><c>elnrng</c> - Link number out of range</item> <item><c>eloop</c> - Too many levels of symbolic links</item> <item><c>emfile</c> - Too many open files</item> <item><c>emlink</c> - Too many links</item> <item><c>emsgsize</c> - Message too long</item> <item><c>emultihop</c> - Multihop attempted</item> <item><c>enametoolong</c> - Filename too long</item> <item><c>enavail</c> - Unavailable</item> <item><c>enet</c> - ENET</item> <item><c>enetdown</c> - Network is down</item> <item><c>enetreset</c> - Network dropped connection on reset</item> <item><c>enetunreach</c> - Network is unreachable</item> <item><c>enfile</c> - File table overflow</item> <item><c>enoano</c> - Anode table overflow</item> <item><c>enobufs</c> - No buffer space available</item> <item><c>enocsi</c> - No CSI structure available</item> <item><c>enodata</c> - No data available</item> <item><c>enodev</c> - No such device</item> <item><c>enoent</c> - No such file or directory</item> <item><c>enoexec</c> - Exec format error</item> <item><c>enolck</c> - No locks available</item> <item><c>enolink</c> - Link has been severed</item> <item><c>enomem</c> - Not enough memory</item> <item><c>enomsg</c> - No message of desired type</item> <item><c>enonet</c> - Machine is not on the network</item> <item><c>enopkg</c> - Package not installed</item> <item><c>enoprotoopt</c> - Bad protocol option</item> <item><c>enospc</c> - No space left on device</item> <item><c>enosr</c> - Out of stream resources or not a stream device</item> <item><c>enosym</c> - Unresolved symbol name</item> <item><c>enosys</c> - Function not implemented</item> <item><c>enotblk</c> - Block device required</item> <item><c>enotconn</c> - Socket is not connected</item> <item><c>enotdir</c> - Not a directory</item> <item><c>enotempty</c> - Directory not empty</item> <item><c>enotnam</c> - Not a named file</item> <item><c>enotsock</c> - Socket operation on non-socket</item> <item><c>enotsup</c> - Operation not supported</item> <item><c>enotty</c> - Inappropriate device for <c>ioctl</c></item> <item><c>enotuniq</c> - Name not unique on network</item> <item><c>enxio</c> - No such device or address</item> <item><c>eopnotsupp</c> - Operation not supported on socket</item> <item><c>eperm</c> - Not owner</item> <item><c>epfnosupport</c> - Protocol family not supported</item> <item><c>epipe</c> - Broken pipe</item> <item><c>eproclim</c> - Too many processes</item> <item><c>eprocunavail</c> - Bad procedure for program</item> <item><c>eprogmismatch</c> - Wrong program version</item> <item><c>eprogunavail</c> - RPC program unavailable</item> <item><c>eproto</c> - Protocol error</item> <item><c>eprotonosupport</c> - Protocol not supported</item> <item><c>eprototype</c> - Wrong protocol type for socket</item> <item><c>erange</c> - Math result unrepresentable</item> <item><c>erefused</c> - EREFUSED</item> <item><c>eremchg</c> - Remote address changed</item> <item><c>eremdev</c> - Remote device</item> <item><c>eremote</c> - Pathname hit remote filesystem</item> <item><c>eremoteio</c> - Remote I/O error</item> <item><c>eremoterelease</c> - EREMOTERELEASE</item> <item><c>erofs</c> - Read-only filesystem</item> <item><c>erpcmismatch</c> - Wrong RPC version</item> <item><c>erremote</c> - Object is remote</item> <item><c>eshutdown</c> - Cannot send after socket shutdown</item> <item><c>esocktnosupport</c> - Socket type not supported</item> <item><c>espipe</c> - Invalid seek</item> <item><c>esrch</c> - No such process</item> <item><c>esrmnt</c> - Srmount error</item> <item><c>estale</c> - Stale remote file handle</item> <item><c>esuccess</c> - Error 0</item> <item><c>etime</c> - Timer expired</item> <item><c>etimedout</c> - Connection timed out</item> <item><c>etoomanyrefs</c> - Too many references</item> <item><c>etxtbsy</c> - Text file or pseudo-device busy</item> <item><c>euclean</c> - Structure needs cleaning</item> <item><c>eunatch</c> - Protocol driver not attached</item> <item><c>eusers</c> - Too many users</item> <item><c>eversion</c> - Version mismatch</item> <item><c>ewouldblock</c> - Operation would block</item> <item><c>exdev</c> - Cross-domain link</item> <item><c>exfull</c> - Message tables full</item> <item><c>nxdomain</c> - Hostname or domain name cannot be found</item> </list> </section> </erlref>