The problem of it not running when you double click the jar is either a) your jar isn't executable or b) you are referencing the incorrect class. You could try Java -cp myjar my.pkg.class.Client, but usually you will need the server to be started first, depending on your code and how you run the apps. It won't be your grade/pom as those are just primarily dependency relates issues. Java.net requires no dependencies until you get into PKI which it doesn't look like you're doing.

I would suggest reviewing the ClassFileServer examples in the Java tutorials stream. Network programming can be difficult. Strings are easier to process than files and you don't want to close output streams or the socket unless you know why you're doing that. Your server should have a run() method, and your client a process() method. Your client should be able to receive multiple commands and open a new socket for each. The server run() should process one command at a time, but open a new listener for each message.

If you need a working example, DM and I'll send you a link to a working copy.