servlet for implementing socket connection

Question

How do I implement a web application with a Servlet that is listening on a port for socket connections?

Solution 1

I assume you don't mean the front-door HTTP connection, which you get for free with the servlet container... But if you want to add, say, an admin service you could create a listener thread that sets some global state in the servlet. Note that this is not considered kosher (and I believe may even violate the servlet standard).

Solution 2

Having the servlet open ServerSockets is a bad code smell. This is primarily because it is the container's responsibility to manage sockets (among other resources like worker threads, sessions etc).

That said, I do not think you need a servlet in the first place. Unless you want to access some of the container's services, it would be better if you use a J2SE application to manage ServerSockets.

Solution 3

Not totally sure what you want to achieve, but you can have a look at client/server programming if that's what you need. Other than that, you could implement your web application as normal but change the default port to whatever suits your need.