recv()

The socket call receives data on a connected socket.

Syntax

#include <types.h>
#include <sys\socket.h>
int recv(s, buf, len, flags)
int s;
char *buf;
int len;
int flags;

Parameters

s

Socket descriptor.

Pointer to the buffer that receives the data.

Length of the buffer in bytes pointed to by the buf parameter.

Permits the call to exercise control over the reception of messages. Set this parameter by specifying one or more of the following flags. If you specify more than one flag, use the logical OR operator (|) to separate them. Setting this parameter is supported only for sockets in the internet domain.

MSG_DONTWAIT

Do not wait for resources or data during this call.
MSG_OOB
Reads any out-of-band data on the socket.
MSG_PEEK
Peeks at the data present on the socket; the data is returned but not consumed, so that a subsequent receive operation sees the same data.
MSG_WAITALL
Wait for data to fill all buffers before returning.

Description

This call receives data on a socket with descriptor s and stores it in the buffer pointed to by buf. The recv() call applies only to connected sockets. For information on how to use recv() with datagram and raw sockets, see Datagram or Raw Sockets.

The recv() call returns the length of the incoming data. If a datagram or sequenced packet is too long to fit in the buffer, the excess is discarded. No data is discarded for stream or sequenced packet sockets. If data is not available at the socket with descriptor s, the recv() call waits for data to arrive and blocks the caller, unless the socket is in nonblocking mode. See ioctl() for a description of how to set nonblocking mode.

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

Return Values

When successful, the number of bytes of data received into the buffer is returned. The value 0 indicates that the connection is closed. The value -1 indicates an error. You can get the specific error code by calling sock_errno() or psock_errno().

Error Code

Description
SOCENOTSOCK
Thesparameterisnotavalidsocketdescriptor .
SOCEFAULT
Usingthebufandlenparameterswouldresultinanattempttoaccessmemoryoutsidethecaller ' saddressspace .
SOCEINTR
Interruptedsystemcall .
SOCEINVAL
Invalidargument .
SOCEWOULDBLOCK
Thesparameterisinnonblockingmodeandnodataisavailabletoreceive ,ortheSO _ RCVTIMEOoptionhasbeensetforsocketsandthetimeoutexpiredbeforeanydataarrivedtoreceive .

Related Calls

connect() getsockopt()
ioctl()
readv()
recvfrom()
recvmsg()
select()
send()
sendmsg()
sendto()
setsockopt()
shutdown()
sock_errno()
socket()
writev()

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