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DCOM Dynamic Port Range: Cannot Connect Locally

aw flag

I have a service on a server that communicates over the network with servers using DCOM on dynamic port range 64535-65535. All firewall rules are in place and we can see the traffic passing successfully with no drops. Windows Firewall is also disabled.

The problem I'm having is that the source is unable to connect to a destination server on port 64535. The ping succeeds but TcpTestSucceeded returns 'False'. I'm aware that you need a service listening on the port at the destination end but we have other servers that are reachable on this port, however, both local and foreign address is local so assume this should be listening by default?

I've run the following connection test on both servers just to confirm whether it's a firewall or local issue: Test-NetConnection localhost -port 64535

I get a TcpTestSucceeded: True for the working one and False for the non-working one so looks like this is a local configuration issue.

What local configuration would affect this?

Massimo avatar
ng flag
Is this Windows RPC? Ports are dynamic then. You should not expect one specific port, open the whole range.
jshizzle avatar
aw flag
I mention above that it's in the dynamic port range and all firewall rules are in place to allow this traffic. All working servers appear to be returning a true reply on this port and further investigation on these show local and foreign address as 0.0.0.0 for the process wininit.exe which I know is a launcher for background applications that are always running. Regardless, a local connection test shows this port as closed so I'm trying to figure what configuration is making this open on some but not on others.
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