Jasmin SMS Gateway - Jasmin is a very complete open source SMS Gateway with many enterprise-class features such as:
SmartSniff - SmartSniff is a packet sniffer that capture TCP/IP packets and display them as sequence of conversations between clients and servers.
Kannel - Open Source WAP and SMS Gateway
socat - socat is a relay for bidirectional data transfer between two independent data channels.
Ozeki NG SMS Gateway - Ozeki NG SMS Gateway is a powerful, reliable and flexible SMS Gateway application.
netcat - Netcat is a featured networking utility which reads and writes data across network connections...