Advanced Debugging

A guide to using Wireshark when debugging complex use such as chained-connections.

Testing Supported Python Versions via Docker

Testing RPyC often requires that you use specific Python versions. Docker will make your life easier when testing RPyC locally, especially when performing packet captures of RPyC communication across Python versions. The current settings will use bind mounts to simplify synchronization of RPyC source code within the containers. So, remember to checkout the commit you desire the containers to use on your host!

If desired, individual containers can be specified started

docker-compose -f ./docker/docker-compose.yml create
docker-compose -f ./docker/docker-compose.yml start rpyc-python-3.7
docker-compose -f ./docker/docker-compose.yml start rpyc-python-3.10

The registry server can be started like so

docker exec rpyc-3.8 /opt/rpyc/bin/rpyc_registry.py

The containers can then be used to test to your hearts desire

docker exec rpyc-3.7 /opt/rpyc/bin/rpyc_classic.py --host 0.0.0.0 &
docker exec -it rpyc-3.10 python -c "import rpyc;conn = rpyc.utils.classic.connect('rpyc-3.7'); conn.modules.sys.stderr.write('hello world\n')"

Tips and Tricks

Display filtering for Wireshark

tcp.port == 18878 || tcp.port == 18879
(tcp.port == 18878 || tcp.port == 18879) && tcp.segment_data contains "rpyc.core.service.SlaveService"

Running the chained-connection unit test

cd tests
python  -m unittest test_get_id_pack.Test_get_id_pack.test_chained_connect

After stopping Wireshark, export specified packets, and open the PCAP. If not already configured, add a custom display column:

Title,        Type,   Fields,     Field Occurrence
Stream Index, Custom, tcp.stream, 0

The stream index column makes it easier to decide which TCP stream to follow. Following a TCP provides a more human readable overview of requests and replies that can be printed as a PDF.

../_images/advanced-debugging-chained-connection-w-wireshark.png