Hi,

I am in the process of programming a transparent proxy server in C on Linux. I have to get some concepts clear.

Browser <--> Proxy <--> ISP

The proxy has two struct sockaddr_ins called proxaddr (which contains the IP address of the proxy - 127.0.0.1) and ispaddr (which contains the gateway IP address of the ISP). My doubt is, once my proxy receives responses from the ISP, how do I transfer it to the browser?

Please help.

Jayanth

The browser should be expecting the response so you just write() to the socket it's connected on.

Hi,

Thanks for that, itsme86!

Now I have another problem. I have this sockaddr_in struct called proxaddr with address 127.0.0.1 and the specified port. The browser communicates to this server using this struct (the socket on which the proxy listens is bound to this address). The problem is, I am not able to use the same address while receiving from the ISP. I get a bind() error here. How do I solve this problem?

Please help.

Jayanth

You should only be bind()'ing one time, to the listening socket that the browser connects to. So you have that listening socket and you do something like select() on it to wait for the browser to connect. As soon as it connects, select() exits and you call accept() which will return the new socket for communication with the browser. Then you can read the data the browser sends on that new socket and parse the data for the request. Then you create a new socket using connect() to serve the request. Once connect() returns you send the request on behalf of the browser and then read() from that socket. When you get data from that one you then write() it to the socket for the browser.