DotNetRemoting SDK for .NET allows to build Bidirectional network applications.
Major features: Bidirectional, Firewall transparancy, Http, TCP, UDP, GPRS, Encryption, serialization. On mobile devices it supports GPRS based connection, Wi-Fi and any other socket based connection. Http based componets support http requests and responses. On PDA it is faster than standard webservices by times (depending on the object sent/received).
Operating System Support: WinXP, Windows2000, Windows2003, Windows CE, Windows Mobile 2005, Pocket PC