4.3BSD-UWisc/man/cat2/send.2

SEND(2)             UNIX Programmer's Manual              SEND(2)



NAME
     send, sendto, sendmsg - send a message from a socket

SYNOPSIS
     #include <sys/types.h>
     #include <sys/socket.h>

     cc = send(s, msg, len, flags)
     int cc, s;
     char *msg;
     int len, flags;

     cc = sendto(s, msg, len, flags, to, tolen)
     int cc, s;
     char *msg;
     int len, flags;
     struct sockaddr *to;
     int tolen;

     cc = sendmsg(s, msg, flags)
     int cc, s;
     struct msghdr msg[];
     int flags;

DESCRIPTION
     _S_e_n_d, _s_e_n_d_t_o, and _s_e_n_d_m_s_g are used to transmit a message to
     another socket.  _S_e_n_d may be used only when the socket is in
     a _c_o_n_n_e_c_t_e_d state, while _s_e_n_d_t_o and _s_e_n_d_m_s_g may be used at
     any time.

     The address of the target is given by _t_o with _t_o_l_e_n specify-
     ing its size.  The length of the message is given by _l_e_n.
     If the message is too long to pass atomically through the
     underlying protocol, then the error EMSGSIZE is returned,
     and the message is not transmitted.

     No indication of failure to deliver is implicit in a _s_e_n_d.
     Return values of -1 indicate some locally detected errors.

     If no messages space is available at the socket to hold the
     message to be transmitted, then _s_e_n_d normally blocks, unless
     the socket has been placed in non-blocking I/O mode.  The
     _s_e_l_e_c_t(2) call may be used to determine when it is possible
     to send more data.

     The _f_l_a_g_s parameter may include one or more of the follow-
     ing:

          #define  MSG_OOB         0x1    /* process out-of-band data */
          #define  MSG_DONTROUTE   0x4    /* bypass routing, use direct interface */
     The flag MSG_OOB is used to send "out-of-band" data on sock-
     ets that support this notion (e.g. SOCK_STREAM); the



Printed 12/27/86          May 14, 1986                          1






SEND(2)             UNIX Programmer's Manual              SEND(2)



     underlying protocol must also support "out-of-band" data.
     MSG_DONTROUTE is usually used only by diagnostic or routing
     programs.

     See _r_e_c_v(2) for a description of the _m_s_g_h_d_r structure.

RETURN VALUE
     The call returns the number of characters sent, or -1 if an
     error occurred.

ERRORS
     [EBADF]             An invalid descriptor was specified.

     [ENOTSOCK]          The argument _s is not a socket.

     [EFAULT]            An invalid user space address was speci-
                         fied for a parameter.

     [EMSGSIZE]          The socket requires that message be sent
                         atomically, and the size of the message
                         to be sent made this impossible.

     [EWOULDBLOCK]       The socket is marked non-blocking and
                         the requested operation would block.

     [ENOBUFS]           The system was unable to allocate an
                         internal buffer.  The operation may
                         succeed when buffers become available.

     [ENOBUFS]           The output queue for a network interface
                         was full.  This generally indicates that
                         the interface has stopped sending, but
                         may be caused by transient congestion.

SEE ALSO
     fcntl(2), recv(2), select(2), getsockopt(2), socket(2),
     write(2)


















Printed 12/27/86          May 14, 1986                          2