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| <h5 class="subsubsection">16.9.5.1 Sending Data</h5> |
| |
| <p><a name="index-sys_002fsocket_002eh-1806"></a>The <code>send</code> function is declared in the header file |
| <samp><span class="file">sys/socket.h</span></samp>. If your <var>flags</var> argument is zero, you can just |
| as well use <code>write</code> instead of <code>send</code>; see <a href="I_002fO-Primitives.html#I_002fO-Primitives">I/O Primitives</a>. If the socket was connected but the connection has broken, |
| you get a <code>SIGPIPE</code> signal for any use of <code>send</code> or |
| <code>write</code> (see <a href="Miscellaneous-Signals.html#Miscellaneous-Signals">Miscellaneous Signals</a>). |
| |
| <!-- sys/socket.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Function: int <b>send</b> (<var>int socket, void *buffer, size_t size, int flags</var>)<var><a name="index-send-1807"></a></var><br> |
| <blockquote><p>The <code>send</code> function is like <code>write</code>, but with the additional |
| flags <var>flags</var>. The possible values of <var>flags</var> are described |
| in <a href="Socket-Data-Options.html#Socket-Data-Options">Socket Data Options</a>. |
| |
| <p>This function returns the number of bytes transmitted, or <code>-1</code> on |
| failure. If the socket is nonblocking, then <code>send</code> (like |
| <code>write</code>) can return after sending just part of the data. |
| See <a href="File-Status-Flags.html#File-Status-Flags">File Status Flags</a>, for information about nonblocking mode. |
| |
| <p>Note, however, that a successful return value merely indicates that |
| the message has been sent without error, not necessarily that it has |
| been received without error. |
| |
| <p>The following <code>errno</code> error conditions are defined for this function: |
| |
| <dl> |
| <dt><code>EBADF</code><dd>The <var>socket</var> argument is not a valid file descriptor. |
| |
| <br><dt><code>EINTR</code><dd>The operation was interrupted by a signal before any data was sent. |
| See <a href="Interrupted-Primitives.html#Interrupted-Primitives">Interrupted Primitives</a>. |
| |
| <br><dt><code>ENOTSOCK</code><dd>The descriptor <var>socket</var> is not a socket. |
| |
| <br><dt><code>EMSGSIZE</code><dd>The socket type requires that the message be sent atomically, but the |
| message is too large for this to be possible. |
| |
| <br><dt><code>EWOULDBLOCK</code><dd>Nonblocking mode has been set on the socket, and the write operation |
| would block. (Normally <code>send</code> blocks until the operation can be |
| completed.) |
| |
| <br><dt><code>ENOBUFS</code><dd>There is not enough internal buffer space available. |
| |
| <br><dt><code>ENOTCONN</code><dd>You never connected this socket. |
| |
| <br><dt><code>EPIPE</code><dd>This socket was connected but the connection is now broken. In this |
| case, <code>send</code> generates a <code>SIGPIPE</code> signal first; if that |
| signal is ignored or blocked, or if its handler returns, then |
| <code>send</code> fails with <code>EPIPE</code>. |
| </dl> |
| |
| <p>This function is defined as a cancellation point in multi-threaded |
| programs, so one has to be prepared for this and make sure that |
| allocated resources (like memory, files descriptors, semaphores or |
| whatever) are freed even if the thread is canceled. |
| <!-- @xref{pthread_cleanup_push}, for a method how to do this. --> |
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