> Well, providing minimal code samples that produce the problem would be > a start.
I prefer an other approach to clarify relevant software configuration differences. > Otherwise we are just guessing... I can offer other data before. > Maybe you have a firewall problem. I hope not. I can try another server variant out as expected. elfring@Sonne:~/Projekte/Python> /usr/bin/python3 test-server2.py & [1] 14067 elfring@Sonne:~/Projekte/Python> /usr/bin/ss -t -l -p -H|grep python LISTEN 0 5 127.0.0.1:search-agent 0.0.0.0:* users:(("python3",pid=14067,fd=3)) elfring@Sonne:~/Projekte/Python> /usr/bin/python3 socket-send_json_data.py --server_id localhost --server_port 1234 Using Python version: 3.7.2 (default, Dec 30 2018, 16:18:15) [GCC] elfring@Sonne:~/Projekte/Python> Result: … Can connections work also with a network service address like “[::1]:35529” (which would be used by the C++ server implementation so far)? How does the software situation look like for the support of the IPv6 loopback address? Regards, Markus -- https://mail.python.org/mailman/listinfo/python-list