recvmsg

 

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 Sockets Library Functions                           recv(3SOCKET)
 
 
 
 NAME
      recv, recvfrom, recvmsg - receive a message from a socket
 
 SYNOPSIS
      cc [ flag ... ] file ... -lsocket  -lnsl [ library ... ]
      #include <sys/types.h>
      #include <sys/socket.h>
      #include <sys/uio.h>
 
      ssize_t recv(int s, void *buf, size_t len, int flags);
 
      ssize_t recvfrom(int s, void *buf, size_t  len,  int  flags,
      struct sockaddr *from, int *fromlen);
 
      ssize_t recvmsg(int s, struct msghdr *msg, int flags);
 
 DESCRIPTION
      recv(), recvfrom(), and recvmsg() are used to  receive  mes-
      sages from another socket. recv() may be used only on a con-
      nected socket (see connect(3SOCKET)), while  recvfrom()  and
      recvmsg() may be used to receive data on a socket whether it
      is in a connected state or not. s is a socket  created  with
      socket(3SOCKET).
 
      If from is not a NULL pointer, the  source  address  of  the
      message  is  filled in. fromlen is a value-result parameter,
      initialized to the size of the buffer associated with  from,
      and  modified  on  return to indicate the actual size of the
      address stored there. The length of the message is returned.
      If  a  message  is  too  long to fit in the supplied buffer,
      excess bytes may be  discarded  depending  on  the  type  of
      socket the message is received from (see socket(3SOCKET)).
 
      If no messages are available at the socket, the receive call
      waits  for  a  message  to arrive, unless the socket is non-
      blocking (see fcntl(2)) in which case -1  is  returned  with
      the external variable errno set to EWOULDBLOCK.
 
      The select() call may be used to determine  when  more  data
      arrives.
 
      The flags parameter is formed by ORing one or  more  of  the
      following:
 
      MSG_OOB
            Read any "out-of-band"  data  present  on  the  socket
            rather than the regular "in-band" data.
 
      MSG_PEEK
            "Peek" at the data present on the socket; the data  is
            returned,  but  not  consumed,  so  that  a subsequent
            receive operation will see the same data.
 
 
 
 SunOS 5.8            Last change: 8 Nov 1999                    1
 
 
 
 
 
 
 Sockets Library Functions                           recv(3SOCKET)
 
 
 
      The recvmsg() call uses a msghdr structure to  minimize  the
      number  of  directly  supplied parameters. This structure is
      defined  in  <sys/socket.h>  and  includes   the   following
      members:
 
 
      caddr_t         msg_name;          /* optional address */
      int             msg_namelen;       /* size of address */
      struct iovec    *msg_iov;          /* scatter/gather array */
      int             msg_iovlen;        /* # elements in msg_iov */
      caddr_t         msg_accrights;     /* access rights sent/received */
      int             msg_accrightslen;
 
           Here msg_name and msg_namelen specify  the  destination
           address  if  the socket is unconnected; msg_name may be
           given as a NULL pointer if  no  names  are  desired  or
           required.  The  msg_iov  and  msg_iovlen  describe  the
           scatter-gather locations, as described in  read(2).   A
           buffer to receive any access rights sent along with the
           message is specified in msg_accrights, which has length
           msg_accrightslen.
 
 
 RETURN VALUES
      These calls return the number of bytes received, or -1 if an
      error occurred.
 
 ERRORS
      The calls fail if:
 
      EBADF s is an invalid file descriptor.
 
      EINTR The operation was interrupted by delivery of a  signal
            before any data was available to be received.
 
      EIO   An I/O error occurred while reading from or writing to
            the file system.
 
      ENOMEM
            There was insufficient user memory available  for  the
            operation to complete.
 
      ENOSR There were insufficient  STREAMS  resources  available
            for the operation to complete.
 
      ENOTSOCK
            s is not a socket.
 
      ESTALE
            A stale NFS file handle exists.
 
      EWOULDBLOCK
 
 
 
 SunOS 5.8            Last change: 8 Nov 1999                    2
 
 
 
 
 
 
 Sockets Library Functions                           recv(3SOCKET)
 
 
 
            The socket is marked non-blocking  and  the  requested
            operation would block.
 
 ATTRIBUTES
      See attributes(5) for descriptions of the  following  attri-
      butes:
 
      ____________________________________________________________
     |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
     |_____________________________|_____________________________|
     | MT-Level                    | Safe                        |
     |_____________________________|_____________________________|
 
 
 SEE ALSO
      fcntl(2),     ioctl(2),      read(2),      connect(3SOCKET),
      getsockopt(3SOCKET),  send(3SOCKET), socket(3SOCKET), attri-
      butes(5), socket(3HEAD)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 SunOS 5.8            Last change: 8 Nov 1999                    3
 
 
 

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