Can't send P2P message from real IP

I need to send messages to Android phones through P2P on 3G connection. Sending and receiving works perfectly on lan ip addresses(on wi-fi) but not on 3g or 2g. On 3g I send a message but it never appears on the other end of the line. Can anyone开发者_如何学JAVA tell me how to make a connection ? What port to use ?

Thanks, DataSmith

DataSmith, what you refer to as internal and external IP address is most probably private IP address and public IP addresses. Private IP address are valid only on the lan where the device is located. This is why you can connect to other peers on the LAN.

However, there is no way you can connect alone to peers on other LANs (unless they have a public IP address on their LAN, which most probably is not the case). You need to learn about IP address translation and NAT traversal to achieve this. You can check the Practical JXTA II book available online for reading at Scribd.