关闭客户端和服务器后的孤立TCP连接

Question

I implemented a client server application in java and it works fine . Now if i do a netstat -a in the shell to see the active connections i see that there are alot of orphaned connections of the following form

TCP 127.0.0.1:54725 Sin-Host:0 LISTENING

For example if i create a server on port 58185 like below

TCP 127.0.0.1:58185 Sin-Host:0 LISTENING

When a client connects to it i get two connections like as follows

TCP 127.0.0.1:58185 Sin-Host:0 LISTENING
TCP 127.0.0.1:58185 Sin-Host:58187 ESTABLISHED
TCP 127.0.0.1:58187 Sin-Host:58185 ESTABLISHED

Now when i close both my client and server the first connection remains ( namely in LISTENING state not TIMED_WAIT )

I think there is no reason for the first connection to remain when i have closed both the client and server . Is this a bug ? It doesnt really affect my program but i just want to know so that i know its impact .

**EDIT : How long do these orphans last**

I rebooted my system and all the orphans are gone . I repeated the test and see that orphans remain even after application shut down but go away after system reboot .

Maybe i guess this is some system settings that prevents it from going in the first place .?

Answer 1

As long as you have a line like

serverSocket.accept();

in you code the connection with LISTENING will remain.

The accept() leads to the LISTENING state of the port.

Both of the ESTABLSHED lines are for the active connection.