CC Proxy can work as RTSP proxy server for Real Player.

CCProxy is an easy-to-use proxy server software. Full supports Windows 98/ME/NT/2000/XP/2003. For more details of CCProxy, please click here. Also you can download it here for a trial. CC Proxy Server allows all computers on the LAN access the Internet through a single Internet connection. You only need to install CC Proxy on the server which can access the Internet directly and other PC clients can connect to the Internet through CC Proxy. It will provide you a cost-effective Internet connection sharing solution without losing ease of use and peace of mind.

Take RealPlayer 8.0 for example:

Proxy server address is 192.168.0.1.
RealPlayer port is 808.

Step1: Menu "View"-->"Preferences"-->"Transport"
Choose "Use specified transports"
Note: Don't choose "Use specific UDP port(s)".

Figure-1

Step 2: Click "RTSP Settings". Check all the three choices under "Use TCP to Connect to Server".

Figure-2

Step3": Choose "PNA Settings" in Figure-1. Check choice "Use HTTP Only".

Figure-3

Step4: Menu "View"-->"Preferences"-->"Proxy"
Check "Use RTSP proxy". Fill 192.168.0.1 in the first blank . Port is 808.
Check "Manually configure HTTP proxy" Fill 192.168.0.1 in the first blank . Port is 808.
Note: Don't choose "Use PNA proxy".

Figure-4