I have a datalogger in my house that monitors the environment and sends it over the web to a server that I can log into and view that data. I want to retrieve the same data simultaneously as it is being sent out so I can write a program to view it instantly. I have been able to log into the port on the datalogger using the Telnet application and see the data that it would be sending out, however when I use Telnet, it no longer goes out over the web, even though I can see the data. Is there a way to capture the data in real time to forward to a viewing program without hindering it from sending over we web.
Yes, you should be able to use a port forwarder to do that. This is code which intercepts the traffic on a port before sending it to its true destination. I used this code very successfully last year at work:
My purposes were slightly different and I didn't want to record the traffic on the line. So you may need a code change.
There are other 'man in the middle' possibilities. TCPTunnel (written in Java) and Microsoft's MSSOAP SDK 3.0 has an application that does this kind of thing. (I think it's called T3). If you have a 'google', you'll probably find something to do the job.
There are some protocols that can detect 'the man in the middle'. The HTTP protocol being used by your web server may be suspicious - you'll have to try it and see.
Be careful about the term 'port forwarding'. This is a different type of 'port forwarding' from enabling your router to forward external requests from the internet to a machine on your local area network.