Prof B Buchanan OBE on Twitter: "Top scanned UDP port on Internet at the current time is 5060 ... the SIP port (voice communications) ... do you know your TCP/UDP ports? Try
belle-sip-error-TCP bind() failed for ::0 port 5060: Address already in use · Issue #78 · BelledonneCommunications/flexisip · GitHub
![firewall - TCP session established even if the server isn't listening on particular port - Network Engineering Stack Exchange firewall - TCP session established even if the server isn't listening on particular port - Network Engineering Stack Exchange](https://i.stack.imgur.com/bWF7e.png)
firewall - TCP session established even if the server isn't listening on particular port - Network Engineering Stack Exchange
![TCP port blocking results for four major Slovenian ISPs. High failure... | Download Scientific Diagram TCP port blocking results for four major Slovenian ISPs. High failure... | Download Scientific Diagram](https://www.researchgate.net/publication/341978499/figure/fig2/AS:961833842245643@1606330466229/TCP-port-blocking-results-for-four-major-Slovenian-ISPs-High-failure-percentages.png)