TCP Forwarding HOWTO
Contents
1. Overview
Starting with version 0.2.1, D-RATS has generic TCP forwarding support. This means you can pipe some TCP traffic across the radio to a remote station. This may be useful for bridging SMTP traffic to a remote location or for doing POP3 for remote mailbox access. In it's native form, this will be rather slow, given that most of the protocols likely to be used in this fashion are very chatty and depend on a lot of back-and-forth handshaking to complete. While you should be prepared for this, the functionality should still be quite useful.
The way it works is that you tell D-RATS on one end that you want to forward a port to a remote system. This means you pick a local port to listen on, which will be forwarded to some other port on a remote machine accessible to the remote station. That remote station must then be configured to accept incoming connections for that port and to forward the traffic to a specific destination host.
2. Setup
To get started, go to File -> Main Settings and click on the Ports tab. You should see this:
2.1. Configuring the client
The client is the computer station connected to a radio that wishes to accept connections on its local network (or from applications on that machine) and forward them across the radio to another machine.
In this example, we will use SMTP. We will assume that D-RATS will:
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Listen for SMTP connections on port 2525 on the local machine
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Send data received on that port to port 25 on the remote machine
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Address this data to the KI4IFW station across the radio link
Click on the Add button under Outgoing and fill in the appropriate information:
Then click OK when finished.
2.2. Configuring the server
The server is the computer station connected to a radio that wishes to forward TCP traffic received from other stations over the radio to a machine on its local network (or to applications on the machine itself).
In this example, as above, we will use SMTP. We assume D-RATS will:
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Receive traffic for port 25 from stations over the radio link
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Send that traffic to port 25 at the mail.foo.com host
Click on the Add button under Incoming and fill in the appropriate information:
Then click OK when finished.
3. Configuring the application
Next, you must configure an application to use the forwarded port. Assuming you are configuring a mail client on the same machine to send mail over the radio link, configure the outgoing server to be localhost on port 2525. You will want to make sure that TLS and SSL are disabled, and probably also want authentication disabled as well. For thunderbird, the outgoing server setup should look like this:
4. Confirming operation
When some application contacts the forwarded port, the radio will establish a socket session to the remote host and begin forwarding traffic. You can verify that this process has begun by checking the Sessions tab on the main window. It should look similar to this:
