To accept connections, a socket is first created with socket(2), a willingness to accept incoming connections and a queue limit for incom-
ing connections are specified with listen(2), and then the connections are accepted with accept(2). The listen call applies only to sock-
ets 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 may receive an error with an indication of ECONNREFUSED, or, if the underlying protocol supports retransmission, the
request may be ignored so that retries may succeed.
A 0 return value indicates success; -1 indicates an error.
The call fails if:
[EBADF] The argument s is not a valid descriptor.
[ENOTSOCK] The argument s is not a socket.
[EOPNOTSUPP] The socket is not of a type that supports the operation listen.