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ZROS Troubleshooting (ZROScore)

When you try to run uv run zroscore and you get an error like this:

zmq.error.ZMQError: Address already in use (addr='tcp://*:5555')

It means that ports 5555 or 5556 (which ZROS uses by default for subscribers and publishers) are occupied by a previous ZROS or Python process that wasn't closed correctly.

Commands to free the ports

You can use any of the following methods from the terminal to kill the process that is using the ports.

This command will immediately find and kill the process using TCP ports 5555 or 5556.

fuser -k 5555/tcp
fuser -k 5556/tcp
(If it says permission denied, add sudo at the beginning: sudo fuser -k 5555/tcp)

Method 2: Closing all ZROSCore and Python processes

If the error is caused specifically because the ZROS broker is still running in the background:

pkill -f zroscore

If your pegasus_bridge.py or pegasus_viva.py scripts got hung (zombies), you can force close all python processes (this will close all active simulations):

pkill -f python

Method 3: Using lsof to find the PID and then kill

If you want to see exactly what is occupying the port before closing it:

  1. Find the process ID (PID): 

    lsof -i :5555
    (Look for the number in the PID column)

  2. Kill the process using its PID (replacing <PID> with the number): 

    kill -9 <PID>