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+<?xml version="1.0" encoding="latin1" ?>
+<!DOCTYPE cref SYSTEM "cref.dtd">
+
+<cref>
+  <header>
+    <copyright>
+      <year>2001</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>ei_connect</title>
+    <prepared>Jakob Cederlund</prepared>
+    <docno></docno>
+    <approved>?</approved>
+    <checked>?</checked>
+    <date>2001-09-01</date>
+    <rev>A</rev>
+    <file>ei_connect.sgml</file>
+  </header>
+  <lib>ei_connect</lib>
+  <libsummary>Communicate with distributed erlang</libsummary>
+  <description>
+    <p>This module enables C programs to communicate with erlang nodes,
+      using the erlang distribution over TCP/IP.</p>
+    <p>A C node appears to Erlang as a
+      <em>hidden node</em>.
+      That is, Erlang processes that know the name of the
+      C node are able to communicate with it in a normal manner, but
+      the node name will not appear in the listing provided by the
+      Erlang function <c><![CDATA[nodes/0]]></c>.</p>
+    <p>The environment variable <c><![CDATA[ERL_EPMD_PORT]]></c> can be used
+      to indicate which logical cluster a C node belongs to.</p>
+  </description>
+
+  <section>
+    <title>Timeout functions</title>
+    <p>Most functions appear in a version with the suffix
+      <c><![CDATA[_tmo]]></c> appended to the function name. Those function take
+      an additional argument, a timeout in <em>milliseconds</em>. The
+      semantics is this; for each communication primitive involved in
+      the operation, if the primitive does not complete within the time
+      specified, the function will return an error and
+      <c><![CDATA[erl_errno]]></c> will be set to <c><![CDATA[ETIMEDOUT]]></c>. With
+      communication primitive is ment an operation on the socket, like
+      <c><![CDATA[connect]]></c>, <c><![CDATA[accept]]></c>, <c><![CDATA[recv]]></c> or <c><![CDATA[send]]></c>.</p>
+    <p>Obviously the timeouts are for implementing fault tolerance,
+      not to keep hard realtime promises. The <c><![CDATA[_tmo]]></c> functions
+      are for detecting non-responsive peers and to avoid blocking on
+      socket operations. </p>
+    <p>A timeout value of <c><![CDATA[0]]></c> (zero), means that timeouts are
+      disabled. Calling a <c><![CDATA[_tmo]]></c>-function with the last argument as
+      <c><![CDATA[0]]></c> is therefore exactly the same thing as calling the
+      function without the <c><![CDATA[_tmo]]></c> suffix.</p>
+    <p>As with all other ei functions, you are <em>not</em> expected
+      to put the socket in non blocking mode yourself in the program. Every
+      use of non blocking mode is embedded inside the timeout
+      functions. The socket will always be back in blocking mode after
+      the operations are completed (regardless of the result). To
+      avoid problems, leave the socket options alone. Ei will handle
+      any socket options that need modification.</p>
+    <p>In all other senses, the <c><![CDATA[_tmo]]></c> functions inherit all 
+      the return values and the semantics from the functions without 
+      the <c><![CDATA[_tmo]]></c> suffix.</p>
+  </section>
+  <funcs>
+    <func>
+      <name><ret>int</ret><nametext>ei_connect_init(ei_cnode* ec, const char* this_node_name, const char *cookie, short creation)</nametext></name>
+      <name><ret>int</ret><nametext>ei_connect_xinit(ei_cnode* ec, const char *thishostname, const char *thisalivename, const char *thisnodename, Erl_IpAddr thisipaddr, const char *cookie, short creation)</nametext></name>
+      <fsummary>Initialize for a connection.</fsummary>
+      <desc>
+        <p>These function initializes the <c><![CDATA[ec]]></c> structure, to
+          identify the node name and cookie of the server. One of them
+          has to be called before other functions that works on the
+          type <c><![CDATA[ei_cnode]]></c> or a file descriptor associated with a
+          connection to another node are used.</p>
+        <p><c><![CDATA[ec]]></c> is a structure containing information about the
+          C-node. It is used in other <c><![CDATA[ei]]></c> functions for
+          connecting and receiving data.</p>
+        <p><c><![CDATA[this_node_name]]></c> is the  registered name of the process
+          (the name before '@').</p>
+        <p><c><![CDATA[cookie]]></c> is the cookie for the node.</p>
+        <p><c><![CDATA[creation]]></c> identifies a specific instance of a C
+          node. It can help prevent the node from receiving messages
+          sent to an earlier process with the same registered name.</p>
+        <p><c><![CDATA[thishostname]]></c> is the name of the machine we're running
+          on. If long names are to be used, it should be fully
+          qualified (i.e. <c><![CDATA[durin.erix.ericsson.se]]></c> instead of
+          <c><![CDATA[durin]]></c>).</p>
+        <p><c><![CDATA[thisalivename]]></c> is the registered name of the process.</p>
+        <p><c><![CDATA[thisnodename]]></c> is the full name of the node,
+          i.e. <c><![CDATA[einode@durin]]></c>.</p>
+        <p><c><![CDATA[thispaddr]]></c> if the IP address of the host.</p>
+        <p>A C node acting as a server will be assigned a creation
+          number when it calls <c><![CDATA[ei_publish()]]></c>.</p>
+        <p>A connection is closed by simply closing the socket. Refer
+          to system documentation to close the socket gracefully (when
+          there are outgoing packets before close).</p>
+        <p>This function return a negative value indicating that an error
+          occurred.</p>
+        <p>Example 1:
+          </p>
+        <code type="none"><![CDATA[
+int n = 0;
+struct in_addr addr;
+ei_cnode ec;
+addr = inet_addr("150.236.14.75");
+if (ei_connect_xinit(&ec,
+                     "chivas",
+                     "madonna",
+                     "[email protected]",
+                     &addr;
+                     "cookie...",
+                     n++) < 0) {
+    fprintf(stderr,"ERROR when initializing: %d",erl_errno);
+    exit(-1);
+}
+        ]]></code>
+        <p>Example 2:
+          </p>
+        <code type="none"><![CDATA[
+if (ei_connect_init(&ec, "madonna", "cookie...", n++) < 0) {
+    fprintf("ERROR when initializing: %d",erl_errno);
+    exit(-1);
+}
+        ]]></code>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_connect(ei_cnode* ec, char *nodename)</nametext></name>
+      <name><ret>int</ret><nametext>ei_xconnect(ei_cnode* ec, Erl_IpAddr adr, char *alivename)</nametext></name>
+      <fsummary>Establishe a connection to an Erlang node</fsummary>
+      <desc>
+        <p>These functions set up a connection to an Erlang node.</p>
+        <p><c><![CDATA[ei_xconnect()]]></c> requires the IP address of the remote
+          host and the alive name of the remote node
+          to be specified. <c><![CDATA[ei_connect()]]></c> provides an alternative
+          interface, and determines the information from the node name
+          provided.</p>
+        <p><c><![CDATA[addr]]></c> is the 32-bit IP address of the remote host.</p>
+        <p><c><![CDATA[alive]]></c> is the alivename of the remote node.</p>
+        <p><c><![CDATA[node]]></c> is the name of the remote node.</p>
+        <p>These functions return an open file descriptor on success, or
+          a negative value indicating that an error occurred --- in
+          which case they will set <c><![CDATA[erl_errno]]></c> to one of:</p>
+        <taglist>
+          <tag><c><![CDATA[EHOSTUNREACH]]></c></tag>
+          <item>The remote host <c><![CDATA[node]]></c> is unreachable</item>
+          <tag><c><![CDATA[ENOMEM]]></c></tag>
+          <item>No more memory available.</item>
+          <tag><c><![CDATA[EIO]]></c></tag>
+          <item>I/O error.</item>
+        </taglist>
+        <p>Additionally, <c><![CDATA[errno]]></c> values from
+          <c><![CDATA[socket]]></c><em>(2)</em> and <c><![CDATA[connect]]></c><em>(2)</em>
+          system calls may be propagated into <c><![CDATA[erl_errno]]></c>.</p>
+        <p>Example:</p>
+        <code type="none"><![CDATA[
+#define NODE   "[email protected]"
+#define ALIVE  "madonna"
+#define IP_ADDR "150.236.14.75"
+
+/*** Variant 1 ***/
+int fd = ei_connect(&ec, NODE);
+
+/*** Variant 2 ***/
+struct in_addr addr;
+addr = inet_addr(IP_ADDR);
+fd = ei_xconnect(&ec, &addr, ALIVE);
+        ]]></code>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_connect_tmo(ei_cnode* ec, char *nodename, unsigned timeout_ms)</nametext></name>
+      <name><ret>int</ret><nametext>ei_xconnect_tmo(ei_cnode* ec, Erl_IpAddr adr, char *alivename, unsigned timeout_ms)</nametext></name>
+      <fsummary>Establish a connection to an Erlang node with optional timeout</fsummary>
+      <desc>
+        <p>ei_connect and ei_xconnect with an optional timeout argument,
+          see the description at the beginning of this document.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_receive(int fd, unsigned char* bufp, int bufsize)</nametext></name>
+      <fsummary>Receive a message</fsummary>
+      <desc>
+        <p>This function receives a message consisting of a sequence
+          of bytes in the Erlang external format.</p>
+        <p><c><![CDATA[fd]]></c> is an open descriptor to an Erlang connection. It
+          is obtained from a previous <c><![CDATA[ei_connect]]></c> or
+          <c><![CDATA[ei_accept]]></c>.</p>
+        <p><c><![CDATA[bufp]]></c> is a buffer large enough to hold the expected
+          message. </p>
+        <p><c><![CDATA[bufsize]]></c> indicates the size of <c><![CDATA[bufp]]></c>.</p>
+        <p>If a <em>tick</em> occurs, i.e., the Erlang node on the
+          other end of the connection has polled this node to see if it
+          is still alive, the function will return <c><![CDATA[ERL_TICK]]></c> and
+          no message will be placed in the buffer. Also,
+          <c><![CDATA[erl_errno]]></c> will be set to <c><![CDATA[EAGAIN]]></c>.</p>
+        <p>On success, the message is placed in the specified buffer
+          and the function returns the number of bytes actually read. On
+          failure, the function returns <c><![CDATA[ERL_ERROR]]></c> and will set
+          <c><![CDATA[erl_errno]]></c> to one of:</p>
+        <taglist>
+          <tag><c><![CDATA[EAGAIN]]></c></tag>
+          <item>Temporary error: Try again.</item>
+          <tag><c><![CDATA[EMSGSIZE]]></c></tag>
+          <item>Buffer too small.</item>
+          <tag><c><![CDATA[EIO]]></c></tag>
+          <item>I/O error.</item>
+        </taglist>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_receive_tmo(int fd, unsigned char* bufp, int bufsize, unsigned timeout_ms)</nametext></name>
+      <fsummary>Receive a message with optional timeout</fsummary>
+      <desc>
+        <p>ei_receive with an optional timeout argument,
+          see the description at the beginning of this document.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_receive_msg(int fd, erlang_msg* msg, ei_x_buff* x)</nametext></name>
+      <name><ret>int</ret><nametext>ei_xreceive_msg(int fd, erlang_msg* msg, ei_x_buff* x)</nametext></name>
+      <fsummary>Receive a message</fsummary>
+      <desc>
+        <p>These functions receives a message to the buffer in
+          <c><![CDATA[x]]></c>.  <c><![CDATA[ei_xreceive_msg]]></c> allows the buffer in
+          <c><![CDATA[x]]></c> to grow, but <c><![CDATA[ei_receive_msg]]></c> fails if the
+          message is bigger than the preallocated buffer in <c><![CDATA[x]]></c>.</p>
+        <p><c><![CDATA[fd]]></c> is an open descriptor to an Erlang connection.</p>
+        <p><c><![CDATA[msg]]></c> is a pointer to an <c><![CDATA[erlang_msg]]></c> structure
+          and contains information on the message received.</p>
+        <p><c><![CDATA[x]]></c> is buffer obtained from <c><![CDATA[ei_x_new]]></c>.</p>
+        <p>On success, the function returns <c><![CDATA[ERL_MSG]]></c> and the
+          <c><![CDATA[msg]]></c> struct will be initialized. <c><![CDATA[erlang_msg]]></c>
+          is defined as follows:</p>
+        <code type="none"><![CDATA[
+typedef struct {
+    long msgtype;
+    erlang_pid from;
+    erlang_pid to;
+    char toname[MAXATOMLEN+1];
+    char cookie[MAXATOMLEN+1];
+    erlang_trace token;
+} erlang_msg;
+        ]]></code>
+        <p><c><![CDATA[msgtype]]></c> identifies the type of message, and is one of
+          <c><![CDATA[ERL_SEND]]></c>, <c><![CDATA[ERL_REG_SEND]]></c>, <c><![CDATA[ERL_LINK]]></c>,
+          <c><![CDATA[ERL_UNLINK]]></c> and <c><![CDATA[ERL_EXIT]]></c>.</p>
+        <p>If <c><![CDATA[msgtype]]></c> is <c><![CDATA[ERL_SEND]]></c> this indicates that an
+          ordinary send operation has taken place, and <c><![CDATA[msg->to]]></c>
+          contains the Pid of the recipient (the C-node). If
+          <c><![CDATA[type]]></c> is <c><![CDATA[ERL_REG_SEND]]></c> then a registered send
+          operation took place, and <c><![CDATA[msg->from]]></c> contains the Pid
+          of the sender.</p>
+        <p>If <c><![CDATA[msgtype]]></c> is <c><![CDATA[ERL_LINK]]></c> or <c><![CDATA[ERL_UNLINK]]></c>, then
+          <c><![CDATA[msg->to]]></c> and <c><![CDATA[msg->from]]></c> contain the pids of the
+          sender and recipient of the link or unlink.</p>
+        <p>If <c><![CDATA[msgtype]]></c> is <c><![CDATA[ERL_EXIT]]></c>, then this indicates that
+          a link has been broken. In this case, <c><![CDATA[msg->to]]></c> and
+          <c><![CDATA[msg->from]]></c> contain the pids of the linked processes.</p>
+        <p>The return value is the same as for <c><![CDATA[ei_receive]]></c>, see
+          above.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_receive_msg_tmo(int fd, erlang_msg* msg, ei_x_buff* x, unsigned imeout_ms)</nametext></name>
+      <name><ret>int</ret><nametext>ei_xreceive_msg_tmo(int fd, erlang_msg* msg, ei_x_buff* x, unsigned timeout_ms)</nametext></name>
+      <fsummary>Receive a message with optional timeout</fsummary>
+      <desc>
+        <p>ei_receive_msg and ei_xreceive_msg with an optional timeout argument,
+          see the description at the beginning of this document.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_receive_encoded(int fd, char **mbufp, int *bufsz,  erlang_msg *msg, int *msglen)</nametext></name>
+      <fsummary>Obsolete function for receiving a message</fsummary>
+      <desc>
+        <p>This function is retained for compatibility with code
+          generated by the interface compiler and with code following
+          examples in the same application.</p>
+        <p>In essence the function performs the same operation as
+          <c><![CDATA[ei_xreceive_msg]]></c>, but instead of using an ei_x_buff, the
+          function expects a pointer to a character pointer
+          (<c><![CDATA[mbufp]]></c>), where the character pointer should point to a
+          memory area allocated by <c><![CDATA[malloc]]></c>. The argument
+          <c><![CDATA[bufsz]]></c> should be a pointer to an integer containing the
+          exact size (in bytes) of the memory area. The function may
+          reallocate the memory area and will in such cases put the new
+          size in <c><![CDATA[*bufsz]]></c> and update <c><![CDATA[*mbufp]]></c>.</p>
+        <p>Furthermore the function returns either ERL_TICK or the
+          <c><![CDATA[msgtype]]></c> field of the <c><![CDATA[erlang_msg *msg]]></c>. The actual
+          length of the message is put in <c><![CDATA[*msglen]]></c>. On error it
+          will return a value <c><![CDATA[< 0]]></c>.</p>
+        <p>It is recommended to use ei_xreceive_msg instead when
+          possible, for the sake of readability. The function will
+          however be retained in the interface for compatibility and
+          will <em>not</em> be removed not be removed in future releases
+          without notice.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_receive_encoded_tmo(int fd, char **mbufp, int *bufsz,  erlang_msg *msg, int *msglen, unsigned timeout_ms)</nametext></name>
+      <fsummary>Obsolete function for receiving a message with timeout</fsummary>
+      <desc>
+        <p>ei_receive_encoded with an optional timeout argument,
+          see the description at the beginning of this document.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_send(int fd, erlang_pid* to, char* buf, int len)</nametext></name>
+      <fsummary>Send a message</fsummary>
+      <desc>
+        <p>This function sends an Erlang term to a process.</p>
+        <p><c><![CDATA[fd]]></c> is an open descriptor to an Erlang connection.</p>
+        <p><c><![CDATA[to]]></c> is the Pid of the intended recipient of the
+          message.</p>
+        <p><c><![CDATA[buf]]></c> is the buffer containing the term in binary
+          format.</p>
+        <p><c><![CDATA[len]]></c> is the length of the message in bytes.</p>
+        <p>The function returns 0 if successful, otherwise -1, in the
+          latter case it will set <c><![CDATA[erl_errno]]></c> to <c><![CDATA[EIO]]></c>.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_send_tmo(int fd, erlang_pid* to, char* buf, int len, unsigned timeout_ms)</nametext></name>
+      <fsummary>Send a message with optional timeout</fsummary>
+      <desc>
+        <p>ei_send with an optional timeout argument,
+          see the description at the beginning of this document.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_send_encoded(int fd, erlang_pid* to, char* buf, int len)</nametext></name>
+      <fsummary>Obsolete function to send a message</fsummary>
+      <desc>
+        <p>Works exactly as ei_send, the alternative name retained for
+          backward compatibility. The function will <em>not</em> be
+          removed without notice.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_send_encoded_tmo(int fd, erlang_pid* to, char* buf, int len, unsigned timeout_ms)</nametext></name>
+      <fsummary>Obsolete function to send a message with optional timeout</fsummary>
+      <desc>
+        <p>ei_send_encoded with an optional timeout argument,
+          see the description at the beginning of this document.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_reg_send(ei_cnode* ec, int fd, char* server_name, char* buf, int len)</nametext></name>
+      <fsummary>Send a message to a registered name</fsummary>
+      <desc>
+        <p>This function sends an Erlang term to a registered process.
+          </p>
+        <p>This function sends an Erlang term to a process.</p>
+        <p><c><![CDATA[fd]]></c> is an open descriptor to an Erlang connection.</p>
+        <p><c><![CDATA[server_name]]></c> is the registered name of the intended
+          recipient.</p>
+        <p><c><![CDATA[buf]]></c> is the buffer containing the term in binary
+          format.</p>
+        <p><c><![CDATA[len]]></c> is the length of the message in bytes.</p>
+        <p>The function returns 0 if successful, otherwise -1, in the
+          latter case it will set <c><![CDATA[erl_errno]]></c> to <c><![CDATA[EIO]]></c>.</p>
+        <p>Example, send the atom "ok" to the process "worker":</p>
+        <code type="none"><![CDATA[
+ei_x_buff x;
+ei_x_new_with_version(&x);
+ei_x_encode_atom(&x, "ok");
+if (ei_reg_send(&ec, fd, x.buff, x.index) < 0)
+    handle_error();
+        ]]></code>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_reg_send_tmo(ei_cnode* ec, int fd, char* server_name, char* buf, int len, unsigned timeout_ms)</nametext></name>
+      <fsummary>Send a message to a registered name with optional timeout</fsummary>
+      <desc>
+        <p>ei_reg_send with an optional timeout argument,
+          see the description at the beginning of this document.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_send_reg_encoded(int fd, const erlang_pid *from, const char *to, const char *buf, int len)</nametext></name>
+      <fsummary>Obsolete function to send a message to a registered name</fsummary>
+      <desc>
+        <p>This function is retained for compatibility with code
+          generated by the interface compiler and with code following
+          examples in the same application.</p>
+        <p>The function works as <c><![CDATA[ei_reg_send]]></c> with one
+          exception. Instead of taking the <c><![CDATA[ei_cnode]]></c> as a first
+          argument, it takes a second argument, an <c><![CDATA[erlang_pid]]></c>
+          which should be the process identifier of the sending process
+          (in the erlang distribution protocol). </p>
+        <p>A suitable <c><![CDATA[erlang_pid]]></c> can be constructed from the
+          <c><![CDATA[ei_cnode]]></c> structure by the following example code:</p>
+        <code type="none"><![CDATA[
+          ei_cnode ec;
+          erlang_pid *self;
+          int fd; /* the connection fd */
+          ...
+          self = ei_self(&ec);
+          self->num = fd;
+        ]]></code>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_send_reg_encoded_tmo(int fd, const erlang_pid *from, const char *to, const char *buf, int len)</nametext></name>
+      <fsummary>Obsolete function to send a message to a registered name with timeout</fsummary>
+      <desc>
+        <p>ei_send_reg_encoded with an optional timeout argument,
+          see the description at the beginning of this document.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_rpc(ei_cnode *ec, int fd, char *mod, char *fun, const char *argbuf, int argbuflen, ei_x_buff *x)</nametext></name>
+      <name><ret>int</ret><nametext>ei_rpc_to(ei_cnode *ec, int fd, char *mod, char *fun, const char *argbuf, int argbuflen)</nametext></name>
+      <name><ret>int</ret><nametext>ei_rpc_from(ei_cnode *ec, int fd, int timeout, erlang_msg *msg, ei_x_buff *x)</nametext></name>
+      <fsummary>Remote Procedure Call from C to Erlang</fsummary>
+      <desc>
+        <p>These functions support calling Erlang functions on remote nodes.
+          <c><![CDATA[ei_rpc_to()]]></c> sends an rpc request to a remote node and
+          <c><![CDATA[ei_rpc_from()]]></c> receives the results of such a call.
+          <c><![CDATA[ei_rpc()]]></c> combines the functionality of these two functions
+          by sending an rpc request and waiting for the results. See also
+          <c><![CDATA[rpc:call/4]]></c>. </p>
+        <p><c><![CDATA[ec]]></c> is the C-node structure previously initiated by a
+          call to <c><![CDATA[ei_connect_init()]]></c> or
+          <c><![CDATA[ei_connect_xinit()]]></c></p>
+        <p><c><![CDATA[fd]]></c> is an open descriptor to an Erlang connection.</p>
+        <p><c><![CDATA[timeout]]></c> is the maximum time (in ms) to wait for
+          results. Specify <c><![CDATA[ERL_NO_TIMEOUT]]></c> to wait forever.
+          <c><![CDATA[ei_rpc()]]></c> will wait infinitely for the answer,
+          i.e. the call will never time out.</p>
+        <p><c><![CDATA[mod]]></c> is the name of the module containing the function
+          to be run on the remote node.</p>
+        <p><c><![CDATA[fun]]></c> is the name of the function to run.</p>
+        <p><c><![CDATA[argbuf]]></c> is a pointer to a buffer with an encoded
+          Erlang list, without a version magic number, containing the
+          arguments to be passed to the function.</p>
+        <p><c><![CDATA[argbuflen]]></c> is the length of the buffer containing the
+          encoded Erlang list.</p>
+        <p><c><![CDATA[msg]]></c> structure of type <c><![CDATA[erlang_msg]]></c> and contains
+          information on the message received. See <c><![CDATA[ei_receive_msg()]]></c>
+          for a description of the <c><![CDATA[erlang_msg]]></c> format.</p>
+        <p><c><![CDATA[x]]></c> points to the dynamic buffer that receives the
+          result. For for <c><![CDATA[ei_rpc()]]></c> this will be the result
+          without the version magic number. For <c><![CDATA[ei_rpc_from()]]></c>
+          the result will return a version magic number and a 2-tuple
+          <c><![CDATA[{rex,Reply}]]></c>.</p>
+        <p><c><![CDATA[ei_rpc()]]></c> returns the number of bytes in the result
+          on success and -1 on failure. <c><![CDATA[ei_rpc_from()]]></c> returns
+          number of bytes or one of <c><![CDATA[ERL_TICK]]></c>, <c><![CDATA[ERL_TIMEOUT]]></c>
+          and <c><![CDATA[ERL_ERROR]]></c> otherwise. When failing,
+          all three functions set <c><![CDATA[erl_errno]]></c> to one of:</p>
+        <taglist>
+          <tag><c><![CDATA[EIO]]></c></tag>
+          <item>I/O error.</item>
+          <tag><c><![CDATA[ETIMEDOUT]]></c></tag>
+          <item>Timeout expired.</item>
+          <tag><c><![CDATA[EAGAIN]]></c></tag>
+          <item>Temporary error: Try again.</item>
+        </taglist>
+        <p>Example, check to see if an erlang process is alive:</p>
+        <code type="none"><![CDATA[
+int index = 0, is_alive;
+ei_x_buff args, result;
+
+ei_x_new(&result);
+ei_x_new(&args);
+ei_x_encode_list_header(&args, 1);
+ei_x_encode_pid(&args, &check_pid);
+ei_x_encode_empty_list(&args);
+
+if (ei_rpc(&ec, fd, "erlang", "is_process_alive",
+           args.buff, args.index, &result) < 0)
+    handle_error();
+
+if (ei_decode_version(result.buff, &index) < 0
+    || ei_decode_bool(result.buff, &index, &is_alive) < 0)
+    handle_error();
+        ]]></code>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_publish(ei_cnode *ec, int port)</nametext></name>
+      <fsummary>Publish a node name</fsummary>
+      <desc>
+        <p>These functions are used by a server process to register
+          with the local name server <em>epmd</em>, thereby allowing
+          other processes to send messages by using the registered name.
+          Before calling either of these functions, the process should
+          have called <c><![CDATA[bind()]]></c> and <c><![CDATA[listen()]]></c> on an open socket.</p>
+        <p><c><![CDATA[ec]]></c> is the C-node structure.</p>
+        <p><c><![CDATA[port]]></c> is the local name to register, and should be the
+          same as the port number that was previously bound to the socket.</p>
+        <p><c><![CDATA[addr]]></c> is the 32-bit IP address of the local host.</p>
+        <p>To unregister with epmd, simply close the returned
+          descriptor. See also <c><![CDATA[ei_unpublish()]]></c>.</p>
+        <p>On success, the functions return a descriptor connecting the
+          calling process to epmd. On failure, they return -1 and set
+          <c><![CDATA[erl_errno]]></c> to <c><![CDATA[EIO]]></c>.</p>
+        <p>Additionally, <c><![CDATA[errno]]></c> values from <c><![CDATA[socket]]></c><em>(2)</em>
+          and <c><![CDATA[connect]]></c><em>(2)</em> system calls may be propagated
+          into <c><![CDATA[erl_errno]]></c>.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_publish_tmo(ei_cnode *ec, int port, unsigned timeout_ms)</nametext></name>
+      <fsummary>Publish a node name with optional timeout</fsummary>
+      <desc>
+        <p>ei_publish with an optional timeout argument,
+          see the description at the beginning of this document.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_accept(ei_cnode *ec, int listensock, ErlConnect *conp)</nametext></name>
+      <fsummary>Accept a connection from another node</fsummary>
+      <desc>
+        <p>This function is used by a server process to accept a
+          connection from a client process.</p>
+        <p><c><![CDATA[ec]]></c> is the C-node structure.</p>
+        <p><c><![CDATA[listensock]]></c> is an open socket descriptor on which
+          <c><![CDATA[listen()]]></c> has previously been called.</p>
+        <p><c><![CDATA[conp]]></c> is a pointer to an <c><![CDATA[ErlConnect]]></c> struct,
+          described as follows:</p>
+        <code type="none"><![CDATA[
+typedef struct {
+  char ipadr[4];             
+  char nodename[MAXNODELEN];
+} ErlConnect;
+        ]]></code>
+        <p>On success, <c><![CDATA[conp]]></c> is filled in with the address and
+          node name of the connecting client and a file descriptor is
+          returned. On failure, <c><![CDATA[ERL_ERROR]]></c> is returned and
+          <c><![CDATA[erl_errno]]></c> is set to <c><![CDATA[EIO]]></c>.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_accept_tmo(ei_cnode *ec, int listensock, ErlConnect *conp, unsigned timeout_ms)</nametext></name>
+      <fsummary>Accept a connection from another node with optional timeout</fsummary>
+      <desc>
+        <p>ei_accept with an optional timeout argument,
+          see the description at the beginning of this document.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_unpublish(ei_cnode *ec)</nametext></name>
+      <fsummary>Unpublish a node name</fsummary>
+      <desc>
+        <p>This function can be called by a process to unregister a
+          specified node from epmd on the localhost. This may be
+          useful, for example, when epmd has not detected the failure of a
+          node, and will not allow the name to be reused. If you use this
+          function to unregister your own process, be sure to also close
+          the descriptor that was returned by <c><![CDATA[ei_publish()]]></c>.</p>
+        <note>
+          <p>Careless use of this function may have unpredictable
+            results, if the registered node is in fact still running.</p>
+        </note>
+        <p><c><![CDATA[ec]]></c> is the node structure of the node to unregister.</p>
+        <p>If the node was successfully unregistered from epmd, the
+          function returns 0. Otherwise, it returns -1 and sets
+          <c><![CDATA[erl_errno]]></c> is to <c><![CDATA[EIO]]></c>.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>int</ret><nametext>ei_unpublish_tmo(ei_cnode *ec, unsigned timeout_ms)</nametext></name>
+      <fsummary>Unpublish a node name with optional timeout</fsummary>
+      <desc>
+        <p>ei_unpublish with an optional timeout argument,
+          see the description at the beginning of this document.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>const char *</ret><nametext>ei_thisnodename(ei_cnode *ec)</nametext></name>
+      <name><ret>const char *</ret><nametext>ei_thishostname(ei_cnode *ec)</nametext></name>
+      <name><ret>const char *</ret><nametext>ei_thisalivename(ei_cnode *ec)</nametext></name>
+      <fsummary>Retrieve some values</fsummary>
+      <desc>
+        <p>These functions can be used to retrieve information about
+          the C Node. These values are initially set with
+          <c><![CDATA[ei_connect_init()]]></c> or <c><![CDATA[ei_connect_xinit()]]></c>.</p>
+        <p>They simply fetches the appropriate field from the <c><![CDATA[ec]]></c>
+          structure. Read the field directly will probably be safe for
+          a long time, so these functions are not really needed.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>erlang_pid *</ret><nametext>ei_self(ei_cnode *ec)</nametext></name>
+      <fsummary>Retrieve the Pid of the C-node</fsummary>
+      <desc>
+        <p>This function retrieves the Pid of the C-node. Every C-node
+          has a (pseudo) pid used in <c><![CDATA[ei_send_reg]]></c>, <c><![CDATA[ei_rpc]]></c>
+          and others. This is contained in a field in the <c><![CDATA[ec]]></c>
+          structure. It will be safe for a long time to fetch this
+          field directly from the <c><![CDATA[ei_cnode]]></c> structure.</p>
+      </desc>
+    </func>
+    <func>
+      <name><ret>struct hostent</ret><nametext>*ei_gethostbyname(const char *name)</nametext></name>
+      <name><ret>struct hostent</ret><nametext>*ei_gethostbyaddr(const char *addr, int len, int type)</nametext></name>
+      <name><ret>struct hostent</ret><nametext>*ei_gethostbyname_r(const char *name,  struct hostent *hostp,  char *buffer,  int buflen,  int *h_errnop)</nametext></name>
+      <name><ret>struct hostent</ret><nametext>*ei_gethostbyaddr_r(const char *addr, int length,  int type,  struct hostent *hostp, char *buffer,   int buflen,  int *h_errnop)</nametext></name>
+      <fsummary>Name lookup functions</fsummary>
+      <desc>
+        <p>These are convenience functions for some common name lookup functions.</p>
+      </desc>
+    </func>
+  </funcs>
+
+  <section>
+    <title>Debug Information</title>
+    <p>If a connection attempt fails, the following can be checked:</p>
+    <list type="bulleted">
+      <item><c><![CDATA[erl_errno]]></c></item>
+      <item>that the right cookie was used</item>
+      <item>that <em>epmd</em> is running</item>
+      <item>the remote Erlang node on the other side is running the
+       same version of Erlang as the <c><![CDATA[ei]]></c>
+       library.</item>
+      <item>the environment variable <c><![CDATA[ERL_EPMD_PORT]]></c>
+       is set correctly.</item>
+    </list>
+  </section>
+</cref>
+