listen - 監聽套接字上的連接

內容簡介

#include <sys/socket.h>

int listen(int sockfd**, int** backlog**);**

描述

To accept connections, a socket is first created with  socket (2), a willingness to accept incoming connections and a queue limit for incoming connections are specified with listen (), and then the connections are accepted with  accept (2). 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 may receive an error with an indication of ECONNREFUSED or, if the underlying protocol supports retransmission, the request may be ignored so that retries succeed.

注意

The behaviour of the  backlog  parameter on TCP sockets changed with Linux 2.2. Now it specifies the queue length for  completely  established sockets waiting to be accepted, instead of the number of incomplete connection requests. The maximum length of the queue for incomplete sockets can be set using the  tcp_max_syn_backlog  sysctl. When syncookies are enabled there is no logical maximum length and this sysctl setting is ignored. See  tcp (7) for more information.

返回值

On success, zero is returned. On error, -1 is returned, and  errno  is set appropriately.

錯誤

標籤

描述

EADDRINUSE

 

Another socket is already listening on the same port.

EBADF

The argument sockfd is not a valid descriptor.

ENOTSOCK

 

The argument sockfd is not a socket.

EOPNOTSUPP

 

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

遵循於

4.4BSD, POSIX.1-2001. The  listen () function call first appeared in 4.2BSD.

BUGS

If the socket is of type  AF_INET , and the  backlog  argument is greater than the constant SOMAXCONN  (128 in Linux 2.0 & 2.2), it is silently truncated to  SOMAXCONN .

另請參閱

• accept (2)

• bind (2)

• connect (2)

• socket (2)