LISTEN(3SOCKET) Sockets Library Functions LISTEN(3SOCKET)

listen - listen for connections on a socket

cc [ flag ... ] file ... -lsocket  -lnsl  [ library ... ]
#include <sys/types.h>
#include <sys/socket.h>
int listen(int s, int backlog);

To accept connections, a socket is first created with socket(3SOCKET), a backlog for incoming connections is specified with listen() and then the connections are accepted with accept(3SOCKET). The listen() call applies only to sockets of type SOCK_STREAM or SOCK_SEQPACKET.

The backlog parameter defines the maximum length the queue of pending connections may grow to.

If a connection request arrives with the queue full, the client will receive an error with an indication of ECONNREFUSED for AF_UNIX sockets. If the underlying protocol supports retransmission, the connection request may be ignored so that retries may succeed. For AF_INET and AF_INET6sockets, the TCP will retry the connection. If the backlog is not cleared by the time the tcp times out, the connect will fail with ETIMEDOUT.

A 0 return value indicates success; −1 indicates an error.

The call fails if:


The argument s is not a valid file descriptor.


The argument s is not a socket.


The socket is not of a type that supports the operation listen().

See attributes(7) for descriptions of the following attributes:

MT-Level Safe

socket.h(3HEAD), accept(3SOCKET), connect(3SOCKET), socket(3SOCKET), attributes(7)

There is currently no backlog limit.

November 8, 1999 OmniOS