What is the cost of many TIME_WAIT on the server side?

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Let's assume there is a client that makes a lot of short-living connections to a server.

If the client closes the connection, there will be many ports in TIME_WAIT state on the client side. Since the client runs out of local ports, it becomes impossible to make a new connection attempt quickly.

If the server closes the connection, I will see many TIME_WAITs on the server side. However, does this do any harm? The client (or other clients) can keep making connection attempts since it never runs out of local ports, and the number of TIME_WAIT state will increase on the server side. What happens eventually? Does something bad happen? (slowdown, crash, dropped connections, etc.)

Please note that my question is not "What is the purpose of TIME_WAIT?" but "What happens if there are so many TIME_WAIT states on the server?" I already know what happens when a connection is closed in TCP/IP and why TIME_WAIT state is required. I'm not trying to trouble-shoot it but just want to know what is the potential issue with it.

To put simply, let's say netstat -nat | grep :8080 | grep TIME_WAIT | wc -l prints 100000. What would happen? Does the OS's network stack slow down? "Too many open files" error? Or, just nothing to worry about?

time-wait tcp networking network-programming
6 Answers

In my scenario i ran a script which schedules files repeatedly,my product do some computations and sends response to client ie client is making a repetitive http call to get the response of each file.When around 150 files are scheduled socket ports in my server goes in time_wait state and an exception is thrown in client which opens a http connection ie

 Error : [Errno 10048] Only one usage of each socket address (protocol/network address/port) is normally permitted

The result was that my application hanged.I do not know may be threadshave gone in wait state or what has happened but i need to kill all processes or restart my application to make it work again.

I tried reducing wait time to 30 seconds since it is 240 seconds by default but it did not work.

So basically overall impact was critical as it made my application non-responsive

user_74676990
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