I am on Windows Server 2016 Standard. See netstat output below (IP replaced):
C:\Users\user>netstat -an|findstr "55559"
TCP 1.2.3.4:55559 1.2.3.4:55559 ESTABLISHED
What does it mean? I was searching the Net for answers but found nothing. Can somebody explain?
UPDATE:
- Process1 was listening on port 55559.
- Process2 connected to it from the same machine (but on its public IP: 10.x.y.z).
(Process1 is an IIS AppPool, which besides its normal OWIN WebApi interface opens an additional tcp service socket on port 55559 for internal purposes.)
- Process1 was terminated by IIS resource management features (not used for a "long time").
The result is the situation described in the question.
The problem is: Process1 cannot be restarted (on first request by IIS), because its initialization fails (cannot bind on port 55559 because another process uses it.)
The another process is: Process2! Why? How?
netstat
with the-abon
switches so you can see which process and executable are responsible for this connection. You can also try to check with Sysinternals TCPView (learn.microsoft.com/en-us/sysinternals/downloads/tcpview).