the listening socket to accept the new connection from
filled in with the address of the peer socket, as known to the communications layer
true: make the accepted socket nonblocking false: leave it blocking
the file descriptor of the accepted socket on success or -1 on failure. On failure errno is set appropriately.
Calls accept() to accept a connection from a listening socket, sets this.fd to the accepted socket file descriptor and memorises the remote address and port.