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network-programmingsocks

How socks protocol is working

Currently I need to implement socks client. According RFC, Socks protocol has two main commands: CONNECT and BIND. CONNECT is used to forward an outbound connection from socks' client to desired Server. BIND is used to forward an inbound connection from desired Server to socks' client.

My client work as follows:

  1. Firstly It makes connection to socks Server, let us call it a "client connection".

  2. After that it issues commands.

I have some misunderstanding with a "client connection" utilisation. Hence, I have the following questions:

  1. A "client connection" could be used only for one CONNECTION command, is that right ? So for each desired communication I need to create a new "client connection" and after that issue command CONNECT.

  2. For BINDing, firstly, i need to issue CONNECT and after issue command BIND. These commands must be issued in a one "client connection", am I right ?

  3. How many inbound connections socks server could receive on BIND socket ? Only one ?

  4. How traffic flows in case of BIND is used ? We have a "client connection" to socks server. For the "client connection" socks server has one connection to desired server and one incoming connection from desired server. Hence, socks server could receive data from two connections. How this traffic is mixed to the "client connection"?

Solution
    1. Yes.
    2. No. BIND is separate from CONNECT. It is for when you want to listen, so you tell the server to listen on your behalf and tell him what port you're listening on.
    3. Pass.
    4. There is only one connection between the client and the SOCKS server. Everything arriving from the client is sent to the 'desired server'. Everything arriving from the 'desired server' is sent to the client. There is nothing to mix. You wouldn't want the client's sends to be sent back to him, would you?