split HTTP and TCP-only (non-HTTP) traffic

Question

Hi,

I have web application that runs on Tomcat (and gets HTTP requests) and some other backend standalone application that gets only TCP. For some reasons, I can use outside only port 8080. So, I need to get all TCP requests (from outside) to port 8080 and forward HTTP ones to web application on Tomcat and all TCP pure requests (that are not HTTP) - to standalone application. Internal forwarding could be done to any port, e.g. 8181 on Tomcat and 8282 on standalone application. Is it possible to setup such configuration? How it could be done?

Thanks in advance.

Answer 1

TCP and HTTP are protocols in different networking stack layer. If you want to use some application to filter HTTP requests, your application should deal with Application-Layer information, not Network-Layer(like TCP/UDP).

Answer 2

I don't see how this can be possible generally. You could look packet-by-packet, but the middle of an http body can be arbitary so you can't just look at the data of each packet

If any particular client will send you either http or general TCP but not both, can you do this by source-IP address? Do you know the addresses of either the servers that will send you http requests or the ones that will send you TCP requests?

If you don't know the source IPs, you could heuristically look at the first packet from some previously unknown IP and see if it looks like http, then tag that address as containing http traffic.

What is the content/format ot the TCP communication? Is there any pattern you can detect in that? Y

Answer 3

Perhaps you could do something like this using iptables + L7 filter. Of course this will only work if you run Linux on your box. Also I don't know how recently l7 filter project has been updated.

Answer 4

Java servlet technology is not limited to Http. The servlet interface lets you read in the incoming input stream via ServletRequest.getInputStream(). So you can create an implementation of Servlet interface and map it in web.xml and you are all set to receive any TCP traffic.

Once you have the read the input stream to sniff the content you will want to forward HTTP requests to an HttpServlet. To do this you will need to make sure that the input stream you pass on is positioned at the very beginning of the input.

EDIT: On reading your question once again, I noticed that you don't plan to expose the Tomcat directly on external port as I originally thought. If you are willing to make the tomcat listen on the external port, you can try the approach described above