recvfrom(2)                    DG/UX R4.11MU05                   recvfrom(2)


NAME
       recvfrom - receive a message from a socket

SYNOPSIS
       #include <sys/socket.h>

       int  recvfrom (s, buf, len, userflags, from, fromlen)
       int  s;
       void * buf;
       int  len;
       int  userflags;
       struct sockaddr *from;
       int * fromlen;

   where:
       s              File descriptor of socket to receive a message from
       buf            Buffer for message
       len            Length of buffer
       userflags     Flags for transfer
       from           Structure to hold sender's name
       fromlen        On input contains the number of bytes available for
                      the sender's name; updated to indicate the number of
                      bytes returned

DESCRIPTION
       The recvfrom call is identical to the recv call with the addition of
       returning the name of the socket from which the message was sent.
       When using recvfrom on connected sockets, the from and fromlen
       arguments will be undefined.  When reading from datagram sockets,
       messages that are longer than the buffer are truncated.  See recv(2)
       for additional information about the socket receive mechanism.

ACCESS CONTROL
       None.

RETURN VALUE
       This call returns the number of bytes received.

       1..len    Number of bytes transferred.

       -1        An error occurred.  errno is set to indicate the error.

DIAGNOSTICS
       Errno may be set to one of the following error codes:

       EBADF     The argument s is not an active valid descriptor.

       ENOTSOCK  The argument s is not a socket.

       EAGAIN    The socket is marked non-blocking and the receive operation
                 would block.

       EINTR     The receive was interrupted by delivery of a signal before
                 any data was available for the receive.

       EFAULT    The data was specified to be received into a non-existent
                 or protected part of the process address space.

       EINVAL    Bad argument.

SEE ALSO
       read(2), recv(2), send(2), socket(2).


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