<?xml version="1.0" encoding="latin1" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>2007</year><year>2009</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
The contents of this file are subject to the Erlang Public License,
Version 1.1, (the "License"); you may not use this file except in
compliance with the License. You should have received a copy of the
Erlang Public License along with this software. If not, it can be
retrieved online at http://www.erlang.org/.
Software distributed under the License is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
the License for the specific language governing rights and limitations
under the License.
</legalnotice>
<title>gen_sctp</title>
<prepared>[email protected]</prepared>
<responsible></responsible>
<docno>1</docno>
<approved></approved>
<checked></checked>
<date>2007-03-21</date>
<rev>A</rev>
<file>gen_sctp.sgml</file>
</header>
<module>gen_sctp</module>
<modulesummary>The gen_sctp module provides functions for communicating with sockets using the SCTP protocol.</modulesummary>
<description>
<p>The <c>gen_sctp</c> module provides functions for communicating with
sockets using the SCTP protocol. The implementation assumes that
the OS kernel supports SCTP
<url href="http://www.rfc-archive.org/getrfc.php?rfc=2960">(RFC2960)</url> through the user-level
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets API Extensions.</url>
During development this implementation was tested on
Linux Fedora Core 5.0 (kernel 2.6.15-2054 or later is needed),
and on Solaris 10, 11. During OTP adaptation it was tested on
SUSE Linux Enterprise Server 10 (x86_64) kernel 2.6.16.27-0.6-smp,
with lksctp-tools-1.0.6, briefly on Solaris 10, and later on
SUSE Linux Enterprise Server 10 Service Pack 1 (x86_64)
kernel 2.6.16.54-0.2.3-smp with lksctp-tools-1.0.7.</p>
<p>Record definitions for the <c>gen_sctp</c> module can be found using:</p>
<pre>
-include_lib("kernel/include/inet_sctp.hrl"). </pre>
<p>These record definitions use the "new" spelling 'adaptation',
not the deprecated 'adaption', regardless of which
spelling the underlying C API uses.</p>
</description>
<section>
<marker id="contents"></marker>
<title>CONTENTS</title>
<list type="bulleted">
<item><seealso marker="#types">DATA TYPES</seealso></item>
<item><seealso marker="#exports">EXPORTS</seealso></item>
<item><seealso marker="#options">SCTP SOCKET OPTIONS</seealso></item>
<item><seealso marker="#examples">SCTP EXAMPLES</seealso></item>
<item><seealso marker="#seealso">SEE ALSO</seealso></item>
<item><seealso marker="#authors">AUTHORS</seealso></item>
</list>
</section>
<section>
<marker id="types"></marker>
<title>DATA TYPES</title>
<marker id="type-assoc_id"></marker>
<taglist>
<tag><c>assoc_id()</c></tag>
<item>
<p>An opaque term returned in for example #sctp_paddr_change{}
that identifies an association for an SCTP socket. The term
is opaque except for the special value <c>0</c> that has a
meaning such as "the whole endpoint" or "all future associations".</p>
<marker id="type-charlist"></marker>
</item>
<tag><c>charlist() = [char()]</c></tag>
<item> <marker id="type-iolist"></marker>
</item>
<tag><c>iolist() = [char() | binary()]</c></tag>
<item> <marker id="type-ip_address"></marker>
</item>
<tag><c>ip_address()</c></tag>
<item>
<p>Represents an address of an SCTP socket.
It is a tuple as explained in
<seealso marker="inet">inet(3)</seealso>.</p>
<marker id="type-port_number"></marker>
</item>
<tag><c>port_number() = 0 .. 65535</c></tag>
<item> <marker id="type-posix"></marker>
</item>
<tag><c>posix()</c></tag>
<item>
<p>See
<seealso marker="inet#error_codes">inet(3); POSIX Error Codes.</seealso></p>
<marker id="type-sctp_option"></marker>
</item>
<tag><c>sctp_option()</c></tag>
<item>
<p>One of the
<seealso marker="#options">SCTP Socket Options.</seealso></p>
<marker id="type-sctp_socket"></marker>
</item>
<tag><c>sctp_socket()</c></tag>
<item>
<p>Socket identifier returned from <c>open/*</c>.</p>
<marker id="type-timeout"></marker>
</item>
<tag><c>timeout() = int() | infinity</c></tag>
<item>
<p>Timeout used in SCTP connect and receive calls.</p>
</item>
</taglist>
<marker id="exports"></marker>
</section>
<funcs>
<func>
<name>abort(sctp_socket(), Assoc) -> ok | {error, posix()}</name>
<fsummary>Abnormally terminate the association given by Assoc, without flushing of unsent data</fsummary>
<type>
<v>Assoc = #sctp_assoc_change{}</v>
</type>
<desc>
<p>Abnormally terminates the association given by <c>Assoc</c>, without
flushing of unsent data. The socket itself remains open. Other
associations opened on this socket are still valid, and it can be
used in new associations.</p>
</desc>
</func>
<func>
<name>close(sctp_socket()) -> ok | {error, posix()}</name>
<fsummary>Completely close the socket and all associations on it</fsummary>
<desc>
<p>Completely closes the socket and all associations on it. The unsent
data is flushed as in <c>eof/2</c>. The <c>close/1</c> call
is blocking or otherwise depending of the value of
the <seealso marker="#option-linger">linger</seealso> socket
<seealso marker="#options">option</seealso>.
If <c>close</c> does not linger or linger timeout expires,
the call returns and the data is flushed in the background.</p>
</desc>
</func>
<func>
<name>connect(Socket, Addr, Port, Opts) -> {ok,Assoc} | {error, posix()}</name>
<fsummary>Same as <c>connect(Socket, Addr, Port, Opts, infinity)</c>.</fsummary>
<desc>
<p>Same as <c>connect(Socket, Addr, Port, Opts, infinity)</c>.</p>
</desc>
</func>
<func>
<name>connect(Socket, Addr, Port, [Opt], Timeout) -> {ok, Assoc} | {error, posix()}</name>
<fsummary>Establish a new association for the socket <c>Socket</c>, with a peer (SCTP server socket)</fsummary>
<type>
<v>Socket = sctp_socket()</v>
<v>Addr = ip_address() | Host</v>
<v>Port = port_number()</v>
<v>Opt = sctp_option()</v>
<v>Timeout = timeout()</v>
<v>Host = atom() | string()</v>
<v>Assoc = #sctp_assoc_change{}</v>
</type>
<desc>
<p>Establishes a new association for the socket <c>Socket</c>,
with the peer (SCTP server socket) given by
<c>Addr</c> and <c>Port</c>. The <c>Timeout</c>,
is expressed in milliseconds.</p>
<p>A socket can be associated with multiple peers.
<marker id="record-sctp_assoc_change"></marker>
The result of <c>connect/*</c> is an <c>#sctp_assoc_change{}</c>
event which contains, in particular, the new
<seealso marker="#type-assoc_id">Association ID:</seealso></p>
<pre>
#sctp_assoc_change{
state = atom(),
error = atom(),
outbound_streams = int(),
inbound_streams = int(),
assoc_id = assoc_id()
} </pre>
<p>The number of outbound and inbound streams can be set by
giving an <c>sctp_initmsg</c> option to <c>connect</c>
as in:</p>
<pre>
connect(Socket, Ip, Port,
[{sctp_initmsg,#sctp_initmsg{num_ostreams=OutStreams,
max_instreams=MaxInStreams}}]) </pre>
<p>All options <c>Opt</c> are set on the socket before the
association is attempted. If an option record has got undefined
field values, the options record is first read from the socket
for those values. In effect, <c>Opt</c> option records only
define field values to change before connecting.</p>
<p>The returned <c>outbound_streams</c> and <c>inbound_streams</c>
are the actual stream numbers on the socket, which may be different
from the requested values (<c>OutStreams</c> and <c>MaxInStreams</c>
respectively) if the peer requires lower values.</p>
<p>The following values of <c>state</c> are possible:</p>
<list type="bulleted">
<item>
<p><c>comm_up</c>: association successfully established. This
indicates a successful completion of <c>connect</c>.</p>
</item>
<item>
<p><c>cant_assoc</c>: association cannot be established
(<c>connect/*</c> failure).</p>
</item>
</list>
<p>All other states do not normally occur in the output from
<c>connect/*</c>. Rather, they may occur in
<c>#sctp_assoc_change{}</c> events received instead of data in
<seealso marker="#recv/1">recv/*</seealso> calls.
All of them indicate losing the association due to various
error conditions, and are listed here for the sake of completeness.
The <c>error</c> field may provide more detailed diagnostics.</p>
<list type="bulleted">
<item>
<p><c>comm_lost</c>;</p>
</item>
<item>
<p><c>restart</c>;</p>
</item>
<item>
<p><c>shutdown_comp</c>.</p>
</item>
</list>
</desc>
</func>
<func>
<name>controlling_process(sctp_socket(), pid()) -> ok</name>
<fsummary>Assign a new controlling process pid to the socket</fsummary>
<desc>
<p>Assigns a new controlling process Pid to Socket. Same implementation
as <c>gen_udp:controlling_process/2</c>.</p>
</desc>
</func>
<func>
<name>eof(Socket, Assoc) -> ok | {error, Reason}</name>
<fsummary>Gracefully terminate the association given by Assoc, with flushing of all unsent data</fsummary>
<type>
<v>Socket = sctp_socket()</v>
<v>Assoc = #sctp_assoc_change{}</v>
</type>
<desc>
<p>Gracefully terminates the association given by <c>Assoc</c>, with
flushing of all unsent data. The socket itself remains open. Other
associations opened on this socket are still valid, and it can be
used in new associations.</p>
</desc>
</func>
<func>
<name>listen(Socket, IsServer) -> ok | {error, Reason}</name>
<fsummary>Set up a socket to listen.</fsummary>
<type>
<v>Socket = sctp_socket()</v>
<v>IsServer = bool()</v>
</type>
<desc>
<p>Sets up a socket to listen on the IP address and port number
it is bound to. IsServer must be 'true' or 'false'.
In the contrast to TCP, in SCTP there is no listening queue length.
If IsServer is 'true' the socket accepts new associations, i.e.
it will become an SCTP server socket.</p>
</desc>
</func>
<func>
<name>open() -> {ok, Socket} | {error, posix()}</name>
<name>open(Port) -> {ok, Socket} | {error, posix()}</name>
<name>open([Opt]) -> {ok, Socket} | {error, posix()}</name>
<name>open(Port, [Opt]) -> {ok, Socket} | {error, posix()}</name>
<fsummary>Create an SCTP socket and bind it to local addresses</fsummary>
<type>
<v>Opt = {ip,IP} | {ifaddr,IP} | {port,Port} | sctp_option()</v>
<v>IP = ip_address() | any | loopback</v>
<v>Port = port_number()</v>
</type>
<desc>
<p>Creates an SCTP socket and binds it to the local addresses
specified by all <c>{ip,IP}</c> (or synonymously <c>{ifaddr,IP}</c>)
options (this feature is called SCTP multi-homing).
The default <c>IP</c> and <c>Port</c> are <c>any</c>
and <c>0</c>, meaning bind to all local addresses on any
one free port.</p>
<p>A default set of socket <seealso marker="#options">options</seealso>
is used. In particular, the socket is opened in
<seealso marker="#option-binary">binary</seealso> and
<seealso marker="#option-active">passive</seealso> mode,
and with reasonably large
<seealso marker="#option-sndbuf">kernel</seealso> and driver
<seealso marker="#option-buffer">buffers.</seealso></p>
</desc>
</func>
<func>
<name>recv(sctp_socket()) -> {ok, {FromIP, FromPort, AncData, BinMsg}} | {error, Reason}</name>
<name>recv(sctp_socket(), timeout()) -> {ok, {FromIP, FromPort, AncData, Data}} | {error, Reason}</name>
<fsummary>Receive a message from a socket</fsummary>
<type>
<v>FromIP = ip_address()</v>
<v>FromPort = port_number()</v>
<v>AncData = [#sctp_sndrcvinfo{}]</v>
<v>Data = binary() | charlist() | #sctp_sndrcvinfo{} |
#sctp_assoc_change{} | #sctp_paddr_change{} |
#sctp_adaptation_event{} </v>
<v>Reason = posix() | #sctp_send_failed{} | #scpt_paddr_change{} |
#sctp_pdapi_event{} | #sctp_remote_error{} |
#sctp_shutdown_event{}</v>
</type>
<desc>
<p>Receives the <c>Data</c> message from any association of the socket.
If the receive times out <c>{error,timeout</c> is returned.
The default timeout is <c>infinity</c>.
<c>FromIP</c> and <c>FromPort</c> indicate the sender's address.</p>
<p><c>AncData</c> is a list of Ancillary Data items which
may be received along with the main <c>Data</c>.
This list can be empty, or contain a single
<seealso marker="#record-sctp_sndrcvinfo">#sctp_sndrcvinfo{}</seealso>
record, if receiving of such ancillary data is enabled
(see option
<seealso marker="#option-sctp_events">sctp_events</seealso>).
It is enabled by default, since such ancillary data
provide an easy way of determining the association and stream
over which the message has been received.
(An alternative way would be to get the Association ID from the
<c>FromIP</c> and <c>FromPort</c> using the
<seealso marker="#option-sctp_get_peer_addr_info">sctp_get_peer_addr_info</seealso> socket option,
but this would still not produce the Stream number).</p>
<p>The actual <c>Data</c> received may be a <c>binary()</c>,
or <c>list()</c> of bytes (integers in the range 0 through 255)
depending on the socket mode, or an SCTP Event.
<marker id="sctp_events"></marker>
The following SCTP Events are possible:</p>
<list type="bulleted">
<item>
<p><seealso marker="#record-sctp_sndrcvinfo">#sctp_sndrcvinfo{}</seealso></p>
</item>
<item>
<p><seealso marker="#record-sctp_assoc_change">#sctp_assoc_change{}</seealso>;</p>
</item>
<item>
<pre>
#sctp_paddr_change{
addr = {ip_address(),port()},
state = atom(),
error = int(),
assoc_id = assoc_id()
} </pre>
<p>Indicates change of the status of the peer's IP address given by
<c>addr</c> within the association <c>assoc_id</c>.
Possible values of <c>state</c> (mostly self-explanatory) include:</p>
<list type="bulleted">
<item>
<p><c>addr_unreachable</c>;</p>
</item>
<item>
<p><c>addr_available</c>;</p>
</item>
<item>
<p><c>addr_removed</c>;</p>
</item>
<item>
<p><c>addr_added</c>;</p>
</item>
<item>
<p><c>addr_made_prim</c>.</p>
</item>
<item>
<p><c>addr_confirmed</c>.</p>
</item>
</list>
<p>In case of an error (e.g. <c>addr_unreachable</c>), the
<c>error</c> field provides additional diagnostics. In such cases,
the <c>#sctp_paddr_change{}</c> Event is automatically
converted into an <c>error</c> term returned by
<c>gen_sctp:recv</c>. The <c>error</c> field value can be
converted into a string using <c>error_string/1</c>.</p>
</item>
<item>
<pre>
#sctp_send_failed{
flags = true | false,
error = int(),
info = #sctp_sndrcvinfo{},
assoc_id = assoc_id()
data = binary()
} </pre>
<p>The sender may receive this event if a send operation fails.
The <c>flags</c> is a Boolean specifying whether the data have
actually been transmitted over the wire; <c>error</c> provides
extended diagnostics, use <c>error_string/1</c>;
<c>info</c> is the original
<seealso marker="#record-sctp_sndrcvinfo">#sctp_sndrcvinfo{}</seealso> record used in the failed
<seealso marker="#send/3">send/*,</seealso> and <c>data</c>
is the whole original data chunk attempted to be sent.</p>
<p>In the current implementation of the Erlang/SCTP binding,
this Event is internally converted into an <c>error</c> term
returned by <c>recv/*</c>.</p>
</item>
<item>
<pre>
#sctp_adaptation_event{
adaptation_ind = int(),
assoc_id = assoc_id()
} </pre>
<p>Delivered when a peer sends an Adaptation Layer Indication
parameter (configured through the option
<seealso marker="#option-sctp_adaptation_layer">sctp_adaptation_layer</seealso>).
Note that with the current implementation of
the Erlang/SCTP binding, this event is disabled by default.</p>
</item>
<item>
<pre>
#sctp_pdapi_event{
indication = sctp_partial_delivery_aborted,
assoc_id = assoc_id()
} </pre>
<p>A partial delivery failure. In the current implementation of
the Erlang/SCTP binding, this Event is internally converted
into an <c>error</c> term returned by <c>recv/*</c>.</p>
</item>
</list>
</desc>
</func>
<func>
<name>send(Socket, SndRcvInfo, Data) -> ok | {error, Reason}</name>
<fsummary>Send a message using an <c>#sctp_sndrcvinfo{}</c>record</fsummary>
<type>
<v>Socket = sctp_socket()</v>
<v>SndRcvInfo = #sctp_sndrcvinfo{}</v>
<v>Data = binary() | iolist()</v>
</type>
<desc>
<p>Sends the <c>Data</c> message with all sending parameters from a
<seealso marker="#record-sctp_sndrcvinfo">#sctp_sndrcvinfo{}</seealso> record.
This way, the user can specify the PPID (passed to the remote end)
and Context (passed to the local SCTP layer) which can be used
for example for error identification.
However, such a fine level of user control is rarely required.
The send/4 function is sufficient for most applications.</p>
</desc>
</func>
<func>
<name>send(Socket, Assoc, Stream, Data) -> ok | {error, Reason}</name>
<fsummary>Send a message over an existing association and given stream</fsummary>
<type>
<v>Socket = sctp_socket()</v>
<v>Assoc = #sctp_assoc_change{} | assoc_id()</v>
<v>Stream = integer()</v>
<v>Data = binary() | iolist()</v>
</type>
<desc>
<p>Sends <c>Data</c> message over an existing association and given
stream.</p>
</desc>
</func>
<func>
<name>error_string(integer()) -> ok | string() | undefined</name>
<fsummary>Translate an SCTP error number into a string</fsummary>
<desc>
<p>Translates an SCTP error number from for example
<c>#sctp_remote_error{}</c> or <c>#sctp_send_failed{}</c> into
an explanatory string, or one of the atoms <c>ok</c> for no
error and <c>undefined</c> for an unrecognized error.</p>
</desc>
</func>
</funcs>
<section>
<marker id="options"></marker>
<title>SCTP SOCKET OPTIONS</title>
<p>The set of admissible SCTP socket options is by construction
orthogonal to the sets of TCP, UDP and generic INET options:
only those options which are explicitly listed below are allowed
for SCTP sockets. Options can be set on the socket using
<c>gen_sctp:open/1,2</c> or <c>inet:setopts/2</c>,
retrieved using <c>inet:getopts/2</c>, and when calling
<c>gen_sctp:connect/4,5</c> options can be changed.</p>
<marker id="option-binary"></marker>
<marker id="option-list"></marker>
<taglist>
<tag><c>{mode, list|binary}</c>or just <c>list</c> or <c>binary</c>.</tag>
<item>
<p>Determines the type of data returned from <c>gen_sctp:recv/1,2</c>.</p>
<marker id="option-active"></marker>
</item>
<tag><c>{active, true|false|once}</c></tag>
<item>
<list type="bulleted">
<item>
<p>If <c>false</c> (passive mode, the default),
the caller needs to do an explicit <c>gen_sctp:recv</c> call
in order to retrieve the available data from the socket.</p>
</item>
<item>
<p>If <c>true</c> (full active mode), the pending data or events are
sent to the owning process.</p>
<p><em>NB:</em> This can cause the message queue to overflow,
as there is no way to throttle the sender in this case
(no flow control!).</p>
</item>
<item>
<p>If <c>once</c>, only one message is automatically placed
in the message queue, after that the mode is automatically
re-set to passive. This provides flow control as well as
the possibility for the receiver to listen for its incoming
SCTP data interleaved with other inter-process messages.</p>
</item>
</list>
<marker id="option-buffer"></marker>
</item>
<tag><c>{buffer, int()}</c></tag>
<item>
<p>Determines the size of the user-level software buffer used by
the SCTP driver. Not to be confused with <c>sndbuf</c>
and <c>recbuf</c> options which correspond to
the kernel socket buffers. It is recommended
to have <c>val(buffer) >= max(val(sndbuf),val(recbuf))</c>.
In fact, the <c>val(buffer)</c> is automatically set to
the above maximum when <c>sndbuf</c> or <c>recbuf</c> values are set.</p>
</item>
<tag><c>{tos, int()}</c></tag>
<item>
<p>Sets the Type-Of-Service field on the IP datagrams being sent,
to the given value, which effectively determines a prioritization
policy for the outbound packets. The acceptable values
are system-dependent. TODO: we do not provide
symbolic names for these values yet.</p>
</item>
<tag><c>{priority, int()}</c></tag>
<item>
<p>A protocol-independent equivalent of <c>tos</c> above. Setting
priority implies setting tos as well.</p>
</item>
<tag><c>{dontroute, true|false}</c></tag>
<item>
<p>By default <c>false</c>. If <c>true</c>, the kernel does not
send packets via any gateway, only sends them to directly
connected hosts.</p>
</item>
<tag><c>{reuseaddr, true|false}</c></tag>
<item>
<p>By default <c>false</c>. If true, the local binding address
<c>{IP,Port}</c> of the socket can be re-used immediately:
no waiting in the CLOSE_WAIT state is performed (may be
required for high-throughput servers).</p>
<marker id="option-linger"></marker>
</item>
<tag><c>{linger, {true|false, int()}</c></tag>
<item>
<p>Determines the timeout in seconds for flushing unsent data in the
<c>gen_sctp:close/1</c> socket call. If the 1st component of the value
tuple is <c>false</c>, the 2nd one is ignored, which means that
<c>gen_sctp:close/1</c> returns immediately not waiting
for data to be flushed. Otherwise, the 2nd component is
the flushing time-out in seconds.</p>
<marker id="option-sndbuf"></marker>
</item>
<tag><c>{sndbuf, int()}</c></tag>
<item>
<p>The size, in bytes, of the *kernel* send buffer for this socket.
Sending errors would occur for datagrams larger than
<c>val(sndbuf)</c>. Setting this option also adjusts
the size of the driver buffer (see <c>buffer</c> above).</p>
</item>
<tag><c>{recbuf, int()}</c></tag>
<item>
<p>The size, in bytes, of the *kernel* recv buffer for this socket.
Sending errors would occur for datagrams larger than
<c>val(sndbuf)</c>. Setting this option also adjusts
the size of the driver buffer (see <c>buffer</c> above).</p>
</item>
<tag><c>{sctp_rtoinfo, #sctp_rtoinfo{}}</c></tag>
<item>
<pre>
#sctp_rtoinfo{
assoc_id = assoc_id(),
initial = int(),
max = int(),
min = int()
} </pre>
<p>Determines re-transmission time-out parameters, in milliseconds,
for the association(s) given by <c>assoc_id</c>.
If <c>assoc_id = 0</c> (default) indicates the whole endpoint. See
<url href="http://www.rfc-archive.org/getrfc.php?rfc=2960">RFC2960</url> and
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets API Extensions for SCTP</url> for the exact semantics of the fields values.</p>
</item>
<tag><c>{sctp_associnfo, #sctp_assocparams{}}</c></tag>
<item>
<pre>
#sctp_assocparams{
assoc_id = assoc_id(),
asocmaxrxt = int(),
number_peer_destinations = int(),
peer_rwnd = int(),
local_rwnd = int(),
cookie_life = int()
} </pre>
<p>Determines association parameters for the association(s) given by
<c>assoc_id</c>. <c>assoc_id = 0</c> (default) indicates
the whole endpoint. See
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets API Extensions for SCTP</url> for the discussion of their semantics. Rarely used.</p>
</item>
<tag><c>{sctp_initmsg, #sctp_initmsg{}}</c></tag>
<item>
<pre>
#sctp_initmsg{
num_ostreams = int(),
max_instreams = int(),
max_attempts = int(),
max_init_timeo = int()
} </pre>
<p>Determines the default parameters which this socket attempts
to negotiate with its peer while establishing an association with it.
Should be set after <c>open/*</c> but before the first
<c>connect/*</c>. <c>#sctp_initmsg{}</c> can also be used
as ancillary data with the first call of <c>send/*</c> to
a new peer (when a new association is created).</p>
<list type="bulleted">
<item>
<p><c>num_ostreams</c>: number of outbound streams;</p>
</item>
<item>
<p><c>max_instreams</c>: max number of in-bound streams;</p>
</item>
<item>
<p><c>max_attempts</c>: max re-transmissions while
establishing an association;</p>
</item>
<item>
<p><c>max_init_timeo</c>: time-out in milliseconds
for establishing an association.</p>
</item>
</list>
<p></p>
</item>
<tag><c>{sctp_autoclose, int()|infinity}</c></tag>
<item>
<p>Determines the time (in seconds) after which an idle association is
automatically closed.</p>
</item>
<tag><c>{sctp_nodelay, true|false}</c></tag>
<item>
<p>Turns on|off the Nagle algorithm for merging small packets
into larger ones (which improves throughput at the expense
of latency).</p>
</item>
<tag><c>{sctp_disable_fragments, true|false}</c></tag>
<item>
<p>If <c>true</c>, induces an error on an attempt to send
a message which is larger than the current PMTU size
(which would require fragmentation/re-assembling).
Note that message fragmentation does not affect
the logical atomicity of its delivery; this option
is provided for performance reasons only.</p>
</item>
<tag><c>{sctp_i_want_mapped_v4_addr, true|false}</c></tag>
<item>
<p>Turns on|off automatic mapping of IPv4 addresses into IPv6 ones
(if the socket address family is AF_INET6).</p>
</item>
<tag><c>{sctp_maxseg, int()}</c></tag>
<item>
<p>Determines the maximum chunk size if message fragmentation is used.
If <c>0</c>, the chunk size is limited by the Path MTU only.</p>
</item>
<tag><c>{sctp_primary_addr, #sctp_prim{}}</c></tag>
<item>
<pre>
#sctp_prim{
assoc_id = assoc_id(),
addr = {IP, Port}
}
IP = ip_address()
Port = port_number() </pre>
<p>For the association given by <c>assoc_id</c>,
<c>{IP,Port}</c> must be one of the peer's addresses.
This option determines that the given address is
treated by the local SCTP stack as the peer's primary address.</p>
</item>
<tag><c>{sctp_set_peer_primary_addr, #sctp_setpeerprim{}}</c></tag>
<item>
<pre>
#sctp_setpeerprim{
assoc_id = assoc_id(),
addr = {IP, Port}
}
IP = ip_address()
Port = port_number() </pre>
<p>When set, informs the peer that it should use <c>{IP, Port}</c>
as the primary address of the local endpoint for the association
given by <c>assoc_id</c>.</p>
<marker id="option-sctp_adaptation_layer"></marker>
</item>
<tag><c>{sctp_adaptation_layer, #sctp_setadaptation{}}</c></tag>
<item>
<marker id="record-sctp_setadaptation"></marker>
<pre>
#sctp_setadaptation{
adaptation_ind = int()
} </pre>
<p>When set, requests that the local endpoint uses the value given by
<c>adaptation_ind</c> as the Adaptation Indication parameter for
establishing new associations. See
<url href="http://www.rfc-archive.org/getrfc.php?rfc=2960">RFC2960</url> and
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets API Extenstions for SCTP</url> for more details.</p>
</item>
<tag><c>{sctp_peer_addr_params, #sctp_paddrparams{}}</c></tag>
<item>
<pre>
#sctp_paddrparams{
assoc_id = assoc_id(),
address = {IP, Port},
hbinterval = int(),
pathmaxrxt = int(),
pathmtu = int(),
sackdelay = int(),
flags = list()
}
IP = ip_address()
Port = port_number() </pre>
<p>This option determines various per-address parameters for
the association given by <c>assoc_id</c> and the peer address
<c>address</c> (the SCTP protocol supports multi-homing,
so more than 1 address can correspond to a given association).</p>
<list type="bulleted">
<item>
<p><c>hbinterval</c>: heartbeat interval, in milliseconds;</p>
</item>
<item>
<p><c>pathmaxrxt</c>: max number of retransmissions
before this address is considered unreachable (and an
alternative address is selected);</p>
</item>
<item>
<p><c>pathmtu</c>: fixed Path MTU, if automatic discovery is
disabled (see <c>flags</c> below);</p>
</item>
<item>
<p><c>sackdelay</c>: delay in milliseconds for SAC messages
(if the delay is enabled, see <c>flags</c> below);</p>
</item>
<item>
<p><c>flags</c>: the following flags are available:</p>
<list type="bulleted">
<item>
<p><c>hb_enable</c>: enable heartbeat; </p>
</item>
<item>
<p><c>hb_disable</c>: disable heartbeat;</p>
</item>
<item>
<p><c>hb_demand</c>: initiate heartbeat immediately;</p>
</item>
<item>
<p><c>pmtud_enable</c>: enable automatic Path MTU discovery;</p>
</item>
<item>
<p><c>pmtud_disable</c>: disable automatic Path MTU discovery;</p>
</item>
<item>
<p><c>sackdelay_enable</c>: enable SAC delay;</p>
</item>
<item>
<p><c>sackdelay_disable</c>: disable SAC delay.</p>
</item>
</list>
<p></p>
</item>
</list>
<p></p>
</item>
<tag><c>{sctp_default_send_param, #sctp_sndrcvinfo{}}</c></tag>
<item>
<marker id="record-sctp_sndrcvinfo"></marker>
<pre>
#sctp_sndrcvinfo{
stream = int(),
ssn = int(),
flags = list(),
ppid = int(),
context = int(),
timetolive = int(),
tsn = int(),
cumtsn = int(),
assoc_id = assoc_id()
} </pre>
<p><c>#sctp_sndrcvinfo{}</c> is used both in this socket option, and as
ancillary data while sending or receiving SCTP messages. When
set as an option, it provides a default values for subsequent
<c>gen_sctp:send</c>calls on the association given by
<c>assoc_id</c>. <c>assoc_id = 0</c> (default) indicates
the whole endpoint. The following fields typically need
to be specified by the sender:</p>
<list type="bulleted">
<item>
<p><c>sinfo_stream</c>: stream number (0-base) within the association
to send the messages through;</p>
</item>
<item>
<p><c>sinfo_flags</c>: the following flags are recognised:</p>
<list type="bulleted">
<item>
<p><c>unordered</c>: the message is to be sent unordered;</p>
</item>
<item>
<p><c>addr_over</c>: the address specified in
<c>gen_sctp:send</c> overwrites the primary peer address;</p>
</item>
<item>
<p><c>abort</c>: abort the current association without
flushing any unsent data;</p>
</item>
<item>
<p><c>eof</c>: gracefully shut down the current
association, with flushing of unsent data.</p>
</item>
</list>
<p></p>
<p>Other fields are rarely used. See
<url href="http://www.rfc-archive.org/getrfc.php?rfc=2960">RFC2960</url> and
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets API Extensions for SCTP</url> for full information.</p>
</item>
</list>
<p></p>
<marker id="option-sctp_events"></marker>
</item>
<tag><c>{sctp_events, #sctp_event_subscribe{}}</c></tag>
<item>
<marker id="record-sctp_event_subscribe"></marker>
<pre>
#sctp_event_subscribe{
data_io_event = true | false,
association_event = true | false,
address_event = true | false,
send_failure_event = true | false,
peer_error_event = true | false,
shutdown_event = true | false,
partial_delivery_event = true | false,
adaptation_layer_event = true | false
} </pre>
<p>This option determines which
<seealso marker="#sctp_events">SCTP Events</seealso> are to be
received (via <seealso marker="#recv/1">recv/*</seealso>)
along with the data. The only
exception is <c>data_io_event</c> which enables or disables
receiving of
<seealso marker="#record-sctp_sndrcvinfo">#sctp_sndrcvinfo{}</seealso>
ancillary data, not events.
By default, all flags except <c>adaptation_layer_event</c> are
enabled, although <c>sctp_data_io_event</c> and
<c>association_event</c> are used by the driver itself and not
exported to the user level.</p>
</item>
<tag><c>{sctp_delayed_ack_time, #sctp_assoc_value{}}</c></tag>
<item>
<pre>
#sctp_assoc_value{
assoc_id = assoc_id(),
assoc_value = int()
} </pre>
<p>Rarely used. Determines the ACK time
(given by <c>assoc_value</c> in milliseconds) for
the given association or the whole endpoint
if <c>assoc_value = 0</c> (default).</p>
</item>
<tag><c>{sctp_status, #sctp_status{}}</c></tag>
<item>
<pre>
#sctp_status{
assoc_id = assoc_id(),
state = atom(),
rwnd = int(),
unackdata = int(),
penddata = int(),
instrms = int(),
outstrms = int(),
fragmentation_point = int(),
primary = #sctp_paddrinfo{}
} </pre>
<p>This option is read-only. It determines the status of
the SCTP association given by <c>assoc_id</c>. Possible values of
<c>state</c> follows. The state designations are mostly
self-explanatory. <c>state_empty</c> is the default which means
that no other state is active:</p>
<list type="bulleted">
<item>
<p><c>sctp_state_empty</c></p>
</item>
<item>
<p><c>sctp_state_closed</c></p>
</item>
<item>
<p><c>sctp_state_cookie_wait</c></p>
</item>
<item>
<p><c>sctp_state_cookie_echoed</c></p>
</item>
<item>
<p><c>sctp_state_established</c></p>
</item>
<item>
<p><c>sctp_state_shutdown_pending</c></p>
</item>
<item>
<p><c>sctp_state_shutdown_sent</c></p>
</item>
<item>
<p><c>sctp_state_shutdown_received</c></p>
</item>
<item>
<p><c>sctp_state_shutdown_ack_sent</c></p>
</item>
</list>
<p>The semantics of other fields is the following:</p>
<list type="bulleted">
<item>
<p><c>sstat_rwnd</c>: the association peer's current receiver
window size;</p>
</item>
<item>
<p><c>sstat_unackdata</c>: number of unacked data chunks;</p>
</item>
<item>
<p><c>sstat_penddata</c>: number of data chunks pending receipt;</p>
</item>
<item>
<p><c>sstat_instrms</c>: number of inbound streams;</p>
</item>
<item>
<p><c>sstat_outstrms</c>: number of outbound streams;</p>
</item>
<item>
<p><c>sstat_fragmentation_point</c>: message size at which SCTP
fragmentation will occur;</p>
</item>
<item>
<p><c>sstat_primary</c>: information on the current primary peer
address (see below for the format of <c>#sctp_paddrinfo{}</c>).</p>
</item>
</list>
<p></p>
<marker id="option-sctp_get_peer_addr_info"></marker>
</item>
<tag><c>{sctp_get_peer_addr_info, #sctp_paddrinfo{}}</c></tag>
<item>
<marker id="record-sctp_paddrinfo"></marker>
<pre>
#sctp_paddrinfo{
assoc_id = assoc_id(),
address = {IP, Port},
state = inactive | active,
cwnd = int(),
srtt = int(),
rto = int(),
mtu = int()
}
IP = ip_address()
Port = port_number() </pre>
<p>This option is read-only. It determines the parameters specific to
the peer's address given by <c>address</c> within the association
given by <c>assoc_id</c>. The <c>address</c> field must be set by the
caller; all other fields are filled in on return.
If <c>assoc_id = 0</c> (default), the <c>address</c>
is automatically translated into the corresponding
association ID. This option is rarely used; see
<url href="http://www.rfc-archive.org/getrfc.php?rfc=2960">RFC2960</url> and
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets API Extensions for SCTP</url> for the semantics of all fields.</p>
</item>
</taglist>
</section>
<section>
<marker id="examples"></marker>
<title>SCTP EXAMPLES</title>
<list type="bulleted">
<item>
<p>Example of an Erlang SCTP Server which receives SCTP messages and
prints them on the standard output:</p>
<pre>
-module(sctp_server).
-export([server/0,server/1,server/2]).
-include_lib("kernel/include/inet.hrl").
-include_lib("kernel/include/inet_sctp.hrl").
server() ->
server(any, 2006).
server([Host,Port]) when is_list(Host), is_list(Port) ->
{ok, #hostent{h_addr_list = [IP|_]}} = inet:gethostbyname(Host),
io:format("~w -> ~w~n", [Host, IP]),
server([IP, list_to_integer(Port)]).
server(IP, Port) when is_tuple(IP) orelse IP == any orelse IP == loopback,
is_integer(Port) ->
{ok,S} = gen_sctp:open([{ip,IP},{port,Port}],[{recbuf,65536}]),
io:format("Listening on ~w:~w. ~w~n", [IP,Port,S]),
ok = gen_sctp:listen(S, true),
server_loop(S).
server_loop(S) ->
case gen_sctp:recv(S) of
{error, Error} ->
io:format("SCTP RECV ERROR: ~p~n", [Error]);
Data ->
io:format("Received: ~p~n", [Data])
end,
server_loop(S). </pre>
<p></p>
</item>
<item>
<p>Example of an Erlang SCTP Client which interacts with the above Server.
Note that in this example, the Client creates an association with
the Server with 5 outbound streams. For this reason, sending of
"Test 0" over Stream 0 succeeds, but sending of "Test 5"
over Stream 5 fails. The client then <c>abort</c>s the association,
which results in the corresponding Event being received on
the Server side.</p>
<pre>
-module(sctp_client).
-export([client/0, client/1, client/2]).
-include_lib("kernel/include/inet.hrl").
-include_lib("kernel/include/inet_sctp.hrl").
client() ->
client([localhost]).
client([Host]) ->
client(Host, 2006);
client([Host, Port]) when is_list(Host), is_list(Port) ->
client(Host,list_to_integer(Port)),
init:stop().
client(Host, Port) when is_integer(Port) ->
{ok,S} = gen_sctp:open(),
{ok,Assoc} = gen_sctp:connect
(S, Host, Port, [{sctp_initmsg,#sctp_initmsg{num_ostreams=5}}]),
io:format("Connection Successful, Assoc=~p~n", [Assoc]),
io:write(gen_sctp:send(S, Assoc, 0, <<"Test 0">>)),
io:nl(),
timer:sleep(10000),
io:write(gen_sctp:send(S, Assoc, 5, <<"Test 5">>)),
io:nl(),
timer:sleep(10000),
io:write(gen_sctp:abort(S, Assoc)),
io:nl(),
timer:sleep(1000),
gen_sctp:close(S). </pre>
<p></p>
</item>
</list>
</section>
<section>
<marker id="seealso"></marker>
<title>SEE ALSO</title>
<p><seealso marker="inet">inet(3)</seealso>,
<seealso marker="gen_tcp">gen_tcp(3)</seealso>,
<seealso marker="gen_udp">gen_upd(3)</seealso>,
<url href="http://www.rfc-archive.org/getrfc.php?rfc=2960">RFC2960</url> (Stream Control Transmission Protocol),
<url href="http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13">Sockets API Extensions for SCTP.</url></p>
<marker id="authors"></marker>
</section>
</erlref>
