RECV(2) — Stardent Computer Inc. (System Calls−BSD)

NAME

recv, recvfrom − receive a message from a socket

SYNOPSIS

#include <sys/types.h>
#include <sys/socket.h>
cc = recv(s, buf, len, flags)
int cc, s;
char ∗buf;
int len, flags;
cc = recvfrom(s, buf, len, flags, from, fromlen)
int cc, s;
char ∗buf;
int len, flags;
struct sockaddr ∗from;
int ∗fromlen;

DESCRIPTION

recv and recvfrom are used to receive messages from a socket.

The recv call is normally used only on a connected socket (see connect(2)), while recvfrom may be used to receive data on a socket whether it is in a connected state or not.

If from is non-zero, 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 in cc. 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(2)).

If no messages are available at the socket, the receive call waits for a message to arrive, unless the socket is nonblocking (see ioctl(2)) in which case a cc of −1 is returned with the external variable errno set to EWOULDBLOCK.

The select(2) call may be used to determine when more data arrives.

The flags argument to a recv call is formed by or’ing one or more of the values,

#defineMSG_OOB0x1/∗ process out-of-band data ∗/

RETURN VALUE

These calls return the number of bytes received, or −1 if an error occurred.

ERRORS

The calls fail if:

[EBADF] The argument s is an invalid descriptor.

[ENOTSOCK] The argument s is not a socket.

[EWOULDBLOCK] The socket is marked non-blocking and the receive operation would block.

[EINTR] The receive was interrupted by delivery of a signal before any data was available for the receive.

[EFAULT] The data was specified to be received into a non-existent or protected part of the process address space.

Museum