Jasmin SMS Gateway - Jasmin is a very complete open source SMS Gateway with many enterprise-class features such as:
netcat - Netcat is a featured networking utility which reads and writes data across network connections...
Ozeki NG SMS Gateway - Ozeki NG SMS Gateway is a powerful, reliable and flexible SMS Gateway application.
PortMapper - Do you need to map a specific TCP or UDP port on your machine to another port on another machine?
Kannel - Open Source WAP and SMS Gateway
Komodia Relay - Free open source tool to perform TCP based session relay