OSF

NAME

recv − Receives messages from connected sockets

SYNOPSIS

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

PARAMETERS

socketSpecifies the socket descriptor. 

bufferPoints to an address where the message should be placed. 

lengthSpecifies the size of the address pointed to by the buffer parameter. 

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

MSG_OOBProcess out-of-band data. 

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

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. 

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

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

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

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

RELATED INFORMATION

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