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(5) for descriptions of the following attributes:
There is currently no backlog limit.