In the previous article, we already saw how to filter on connections. For example when the user manually interrupts a huge data transfer. The TCP session is sending packets as fast as possible, so when the client sends the FIN and closes its part, the server is still sending lots of data for a moment. In this case, the client sends RST packets until the server stops sending data.
It is also important to note that some applications do not close sessions properly and simply use an RST to close every session. While this is not a good practice, you must be aware that some applications are developed this way. We have seen how closing a TCP connection can be more complex than opening one. However, RST packets can also be sent without any connection.
It is also able to graph all the metrics over time, especially the RST per connection. As we saw in the first article , we can use pages like Top Client Zone and Top Servers toanalyzee where the issue is from.
In a next article, we will have a look at how TCP retransmission works, and when it can be an issue or not. In the meantime; if you would like to give it a try, just download our evaluation virtual appliance or download our troubleshooting guide. So all you really need is either for Windows to provide an API that allows this directly, or for someone to have written a program that operates somewhat like a VPN or Fiddler and gives you a way to close sockets that pass through it.
There is at least one program CurrPorts that does exactly this and I used it today for the purpose of closing specific sockets on a process that was started before CurrPorts was started. To do this you must run it as administrator, of course. Note that it is probably not easily possible to cause a program to not listen on a port well, it is possible but that capability is referred to as a firewall I believe the question is "how do I selectively close one active connection socket to the port my program is listening on?
The wording of the question is a bit off because a port number for the undesired inbound client connection is given and it was referred to as "port" but it's pretty clear that it was a reference to that one socket and not the listening port. Note: This answer is huntharo and JasonXA's answer and comment put together and simplified to make it easier for readers. Examples come from CurrPorts' web page.
You can't close sockets without shutting down the process that owns those sockets. Sockets are owned by the process that opened them. Use netstat like so:. Where -a prints all sockets, -n shows the port number, -p shows the PID, -l shows only what's listening this is optional depending on what you're after. Kill literally kills just that process and any children it owns. Using the service command runs the shutdown script registered in the init.
If you use kill on a service it might not properly start back up because you didn't shut it down properly. It just depends on the service.
You can't use netstat. Read this tutorial if you're interested in Mac:. You can't close sockets on your server without owning those sockets hence you can't actually close the socket down without having code running in the process that owns the server socket. However, there is another option which is telling the client to close its socket. You can do that with RST scanning using nmap.
I found the right answer to this one. It does have issues with servers with large number of connections sometimes though. I sometimes use tcpview for interactive kills but wkillcx can be used in scripts. I guess it can help you a lot on both monitoring and killing unwanted connection. In order to close the port you could identify the process that is listening on this port and kill this process. We could not kill the process either, as to not drop other connections.
What we ended up doing and was not suggested yet was to block the connection on Windows' Firewall. Yes, this will block all connections that fit the rule, but in our case there was a single connection the one we were interested in :. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 9 years, 10 months ago. Active 6 months ago. Viewed k times. Improve this question. Victor Stafusa Victor Stafusa 13k 11 11 gold badges 55 55 silver badges 68 68 bronze badges.
You can't close ports from the command line, or files either. You have to close the programs that own them. From the list of inbound rules, find the rule for the port you wish to close. Administration Start or stop services on Windows Disable service auto-start on Windows Open or close server ports Upgrade the stack Backup or restore a stack Uninstall the stack Improve server performance.
Open or close server ports Open server ports for remote access In many cases, it is necessary to open additional ports for your application s to function correctly.
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