To compile the server do:
$ javac Server.java
To run the server do:
$ java Server
Server must be running to get a response, so run both Server and Client simultaneously.
To compile the Client do:
$ javac Client.java
To run the Client do:
$ java Client
Now in server side enter the path of the file that needed to be transferred
Ex : /Users/user/Desktop/anyfile.txt
In Client side enter the path of the file where you wanted to save.
Ex : /Users/user/Desktop/anyfile.txt