Proxy Server Port 3128
Proxy Server Port: 3128
The proxy server acts as a go between for websites and web browsers. It works by listening on a specific port number on the proxy server. Web browsers have to know which port it is, or they won't know how to connect to the proxy server.
Some port numbers are popular. Port 3128 is the default port for the Squid proxy server. Port 8080 is the default port for the Microsoft ISA proxy server.
Once the proxy server administrator configures a port number for the proxy server, the web browser is configured to use the proxy server's port number and host name to browse the web.
Proxy server administrators do not use the default ports, because hackers know and attack them.
A PAC file (Proxy Auto Configuration) is often used by web browsers to automate configuration. A web browser fetches the PAC file to determine the proxy server's port number and other configuration.