网络状态诊断工具——netstat命令

LISTEN ：首先服务端需要打开一个socket进行监听，状态为LISTEN./The socket is listening for incoming? connections. 侦听来自远方TCP端口的连接请求 /
SYN_SENT：客户端通过应用程序调用connect进行activeopen.于是客户端tcp发送一个SYN以请求建立一个连接.之后状态SYN_SENT。/The socket is actively attempting to establish aconnection. 在发送连接请求后等待匹配的连接请求 /
SYN_RECV：服务端应发出ACK确认客户端的 SYN,同时自己向客户端发送一个SYN.之后状态置为SYN_RECV/* A connection request has been received from the network. 在收到和发送一个连接请求后等待对连接请求的确认 /
ESTABLISHED：代表一个打开的连接，双方可以进行或已经在数据交互了。/?The?socket?has?an?established?connection.?代表一个打开的连接，数据可以传送给用户?/
FIN_WAIT1：主动关闭(activeclose)端应用程序调用close，于是其TCP发出FIN请求主动关闭连接，之后进入FIN_WAIT1状态./?The?socket?is?closed,?and?the?connection?is?shutting?down.?等待远程TCP的连接中断请求，或先前的连接中断请求的确认?/
CLOSE_WAIT：被动关闭(passiveclose)端TCP接到FIN后，就发出ACK以回应FIN请求(它的接收也作为文件结束符传递给上层应用程序),并进入CLOSE_WAIT./ The remote end has shut down, waiting for the socketto close. 等待从本地用户发来的连接中断请求 /
FIN_WAIT2：主动关闭端接到ACK后，就进入了FIN-WAIT-2./ Connection is closed, and the socket is waiting for a shutdownfrom the remote end. 从远程TCP等待连接中断请求 /
LAST_ACK：被动关闭端一段时间后，接收到文件结束符的应用程 序将调用CLOSE关闭连接。这导致它的TCP也发送一个 FIN,等待对方的ACK.就进入了LAST-ACK./ The remote end has shut down, and the socket is closed. Waiting foracknowledgement. 等待原来发向远程TCP的连接中断请求的确认 /
TIME_WAIT：在主动关闭端接收到FIN后，TCP 就发送ACK包，并进入TIME-WAIT状态。/ Thesocket is waiting after close to handle packets still in the network.等待足够的时间以确保远程TCP接收到连接中断请求的确认/
CLOSING：比较少见./?Bothsockets?are?shut?down?but?we?still?don’t?have?all?our?datasent.?等待远程TCP对连接中断的确认?/
CLOSED：被动关闭端在接受到ACK包后，就进入了closed的状态。连接结束./The?socket?is?not?being?used.?没有任何连接状态?/
UNKNOWN：未知的Socket状态。/?Thestate?of?the?socket?is?unknown.?*/