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windows-7tcpprocessnetwork-programmingport

process 0 is using my port

I am running a server program that listens on port 2811, and a few clients that communicate on that port. When I run netstat from the command line to see which process is using port 2811, I get that process 0 is also using it:

C:>netstat -ano | find ":2811"
TCP    0.0.0.0:2811           0.0.0.0:0              LISTENING       5448
TCP    127.0.0.1:62391        127.0.0.1:2811         TIME_WAIT       0
TCP    127.0.0.1:62392        127.0.0.1:2811         TIME_WAIT       0

... about 20 more similar lines with pid=0. Then:

TCP    192.168.50.64:2811     192.168.50.64:62237    ESTABLISHED     5448
TCP    192.168.50.64:2811     192.168.50.64:62262    ESTABLISHED     5448
TCP    192.168.50.64:2811     192.168.50.64:62434    ESTABLISHED     5448
TCP    192.168.50.64:62237    192.168.50.64:2811     ESTABLISHED     9472
TCP    192.168.50.64:62262    192.168.50.64:2811     ESTABLISHED     7640
TCP    192.168.50.64:62434    192.168.50.64:2811     ESTABLISHED     5076

If I understand correctly, process 0 is the idle process and it does nothing. So why should it be using my port?

Solution

  • Because the port is in TIME-WAIT state, which means it has been closed by both peers and is just timing out per RFC 793. So no actual process is attributable to it, so its PID shows as zero.