PicoPhone is a simple Internet phone application with chat. If you want a more advanced application, that has also video, File Transfer, address book, that can call regular phones, Send SMS messages to cellphones and more, take v-Phone.
I made Picophone, because all the Internet phones around are quite heavy and use complicated protocols, such as H.323, which has problems with NAPT routers. PicoPhone uses a simple UDP-based protocol, which works very well with NAPT. The program accepts connections on UDP port 11676 and makes connection to that port. Optionally a port number can follow the address (the colon is used as a separator), if the connection has to be made to another port (the NAPT router on the receiving side should convert the port number to the Default 11676).
PicoPhone allows multiple concurrent calls, but the audio device should allow multiple output streams to be opened simultaneously.
