UDP and TCP protocol (AlphaNet)

Originally the intention was to run AlphaNet data over the TCP protocol. And in the filter settings the AlphaNet data was listed in TCP. However, there were some technically challenges to use TCP, and the AlphaNet data was changed to use the UDP protocol instead. But the filter settings in AlphaWeb was not updated to reflect this before AMC 10.21. As from AMC 10.21 the filter setting will show AlphaNet data on UDP, but only after an autoload. So if you autoload a board with 10.20, and upgrade to 10.22 the filter will still show TCP. If you now make an autoload it will show UDP.

The AlphaNet will however work regardless if the AlphaNet data is enabled or not in the firewall. This is because the idle frames of the AlphaNet data protocol which are sent as UDP messages will punch a pinhole in the firewall, and return data can be received on the same port. (A firewall will allow incoming traffic on the same port it transmits, see http://en.wikipedia.org/wiki/Firewall_pinhole).

So all AMC 10.00 - 10.3x versions use UDP for AlphaNet data, although the filter settings might show something else.

As from AMC 10.40 the AlphaNet data is changed back to the original idea, using TCP. The obstacles found in the beginning of the AMC-IP development are overcome, and TCP is a much more suitable and reliable protocol for AlphaNet signaling. In 10.40 the AlphaWeb filter settings are updated accordingly and show AlphaNet data on TCP (AlphaNet audio, and all other VoIP audio, is using UDP). When using TCP it is vital that the TCP port is enabled in the filter settings, if not AlphaNet will not work. Actually it is sufficient to open TCP port 50000 at the node with the higher node number, as this side acts as the "Server" (and the lower node acts as the "Client") in the TCP session.