Index for Section 2

Alphabetical listing for R

Bottom of page

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

SYNOPSIS
  #include <sys/socket.h>

  ssize_t recv(
	  int socket,
	  void *buffer,
	  size_t length,
	  int options );

  [Tru64 UNIX]	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 options );

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

  recv(): XNS4.0, XNS5.0

  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.

  options
      Points to a value controlling the message reception. The options
      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
  [Tru64 UNIX]	The recv() function is identical to the recvfrom() function
  with a zero-valued address_len parameter, and to the read() function if no
  options 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. If no messages are available and the peer has closed the
  connection, the recv() function returns a value of 0. Otherwise, the
  function returns a value of -1 and sets errno to indicate the error.

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

  [EACCES]
      The read() would cause the information label of the process to float to
      an information level that is not dominated by the process's sensitivity
      level.

  [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 option is set and no out-of-band data is available.

  [EIO]
      An I/O error occurred while reading from or writing to the file system.

  [ENOBUFS]
      Insufficient resources were available in the system to complete the
      call.

  [ENOMEM]
      The system did not have sufficient memory to fulfill the request.

  [ENOSR]
      The available STREAMS resources were insufficient for the operation to
      complete.

  [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 options 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.

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

  Standards: standards(5)

  Network Programmer's Guide

Index for Section 2

Alphabetical listing for R

Top of page