I run netstat -o in CMD and found Firefox has some TCP connection in my PC that are odd!
There are two connection between 127.0.0.1(localhost) and Jessica-PC(my computer name) and I think they are equal ! (127.0.0.1 = Jessica-PC)
I test netstat -a and most of Foreign Address are "Jessica-PC"!
What is usage of such connections?
Why firefox need such TCP connections?
I've stumbled over these kind of connections too when developing a web proxy and the answer was surprising. There are some external web sites which try to communicate with a web server on the localhost in order to interact with some local application. A typical example is Spotify (but there are others), which even have DNS setup in a way so that whatever.spotilocal.com resolves to 127.0.0.1, see What is the advantage of having a domain name (spotilocal) that resolves to 127.0.0.1? for more information.
Of course this does not work if proxies are involved, because this would mean to connect to the localhost on the proxy which proxies usually deny for security reasons anyway. And this kind of setup might even be a security risk, since other applications might run a server on localhost, notably the print server CUPS on localhost:631 on Mac an most Linux systems. For details about this long known problem see this article from Tavis Ormandy from 2008.
