Static Port Causing CPotelcol to Fail to Start

[Bob_Zimmerman]

I rolled out a new Skyline config to a bunch of systems recently, and several didn't actually start sending telemetry. Troubleshooting them today, and thought I would share information which seems to be missing from the guides and SKs.

On the first one, I found /opt/CPotelcol/otelcol.log was about 40 MB and had last been written in March. I tried manually stopping and starting CPotelcol using '/opt/CPotelcol/stop' and '/opt/CPotelcol/start'. Still no log data.

I rotated the log file manually using the command 'mv /opt/CPotelcol/otelcol.log{,.2026-03-04}' and ran '/opt/CPotelcol/start'. Still no telemetry, but at least I got log data! A tail of the log shows the message {"kind": "extension", "name": "health_check", "error": "failed to bind to address 127.0.0.1:65533: listen tcp 127.0.0.1:65533: bind: address already in use"}.

Okay, why can't it bind to the port? Most likely cause is something else listening. Ran 'netstat -anp | grep 65533' and sure enough fwd was already listening on that port. This particular system happens to be an MDS, so I got the PID and used 'ps -fp <PID>' to find which CMA owned that fwd. I restarted it ('mdsstop_customer <CMA name> && mdsstart_customer <CMA name>'), then ran '/opt/CPotelcol/start' again. This time, it started, and my telemetry destination started receiving data.

Looks like port 65533 is hard-coded in $CPOTELCOL_DIR/config.json, but other things can get there first. If Skyline is just mysteriously not working for you, check to be sure nothing else has grabbed the port.

[PhoneBoy]

Good tip!

[David_Evans]

+1  This happened to our MDS starting a few months ago.  Now I don't remember exactly how I fixed it.  It seems like I found the range that fwd was set to and excluded the skyline port.

[JozkoMrkvicka]

127.0.0.1:65533 was statically hard-coded in CPotelcol config file. The same localhost and same port is used on MDS for fwd, thus the conflict (port is indeed already in use).

Workaround was to manually change the port in CPotelcol config file to different one, not used by any other process.

Check Point just recently released CPotelcol Take 232 where this bug is finally fixed.

Update CPotelcol to Take 232 and Skyline on MDS will work.