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recv(2)
NAME
  recv - Receives messages from connected sockets

SYNOPSIS
  #include <sys/socket.h>
  ssize_t recv (
	  int socket,
	  void *buffer,
	  size_t length,
	  int flags );

  [Digital]  The following definition of the recv() function  does not
  conform to current standards and is supported only for backward
  compatibility (see standards(5)):

  #include <sys/socket.h>
  int recv (
	  int socket,
	  char *buffer,
	  int length,
	  int flags );

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  recv():  XPG4-UNIX

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  socket    Specifies the socket descriptor.

  buffer    Points to a buffer where the message should be placed.

  length    Specifies the size of the buffer pointed to by the buffer
	    parameter.

  flags	    Points to a value controlling the message reception.  The flags
	    parameter is formed by logically ORing one or more of the
	    following values, defined in the sys/socket.h file:

	    MSG_PEEK  Peek at incoming message.	 The data is treated as
		      unread and the next recv() function (or similar
		      function) will still return this data.

	    MSG_OOB   Process out-of-band data.

	    MSG_WAITALL
		      Requests that the function block wait until the full
		      amount of data requested can be returned.	 The function
		      may return a smaller amount of data if a signal is
		      caught, the connection is terminated, or an error is
		      pending for the socket.

DESCRIPTION
  The recv() function receives messages from a connected socket.  The
  recvfrom() and recvmsg() functions receive messages from both connected and
  unconnected sockets; however, they are usually used for unconnected sockets
  only.

  The recv() function returns the length of the message.  If a message is too
  long to fit in the supplied buffer, excess bytes may be truncated depending
  on the type of socket that issued the message.

  If no messages are available at the socket, the recv() function waits for a
  message to arrive, unless the socket is nonblocking.	If a socket is
  nonblocking, errno is set to [EWOULDBLOCK].

  Use the select() function to determine when more data arrives.

NOTES
  [Digital] The recv() function is identical to the recvfrom() function with
  a zero-valued address_len parameter, and to the read() function if no flags
  are used.  For that reason the recv() function is disabled when 4.4BSD
  behavior is enabled; that is, when the _SOCKADDR_LEN compile-time option is
  defined.

RETURN VALUES
  Upon successful completion, the recv() function returns the length of the
  message in bytes.  Otherwise, a value of -1 is returned, and errno is set
  to indicate the error.

ERRORS
  If the recv() function fails, errno may be set to one of the following
  values:

  [EBADF]   The socket parameter is not valid.

  [ECONNRESET]
	    A connection was forcibly closed by a peer.

  [EFAULT]  The data was directed to be received into a nonexistent or
	    protected part of the process address space.  The buffer
	    parameter is invalid.

  [EINTR]   A signal interrupted the recv() function before any data was
	    available.

  [EINVAL]  The MSG_OOB flag  is set and no out-of-band data is available.

  [ENOTCONN]
	     Receive is attempted on a connection-oriented socket that is not
	    connected.

  [ENOTSOCK]
	    The socket parameter refers to a file, not a socket.

  [EOPNOTSUPP]
	    The specified flags are not supported for this socket type or
	    protocol.

  [ETIMEDOUT]
	    The connection timed out during connection establishment or due
	    to a transmission timeout on active connection.

  [EWOULDBLOCK]
	    The socket is marked nonblocking, and no data is waiting to be
	    received.

RELATED INFORMATION
  Functions: recvfrom(2), recvmsg(2), send(2), sendmsg(2), sendto(2),
  select(2), shutdown(2), socket(2), read(2), write(2)

  Standards: standards(5)