Always Run ***Server.java first then ****client.java source code All code was run successfully (without any Warning) in Linux Mint Eclipse Oxygen2.0 on OpenJDK environment. The Problems may arise in Windows System as they Block the Port.This shitty things can be reduced by 2 ways. One of them is, the server code and the client code will be run only Once on the first time when you RUN it.and after each run you have to change your port number.9900 9090 8907 4567 etc etc or 'Gogol' it for "Unblocking Port in windows"[this is somewhere in system32 or Windows folder in OS drive ] Other problem may be occured in File_Server/File_Client as i didn't use Inet() function. If this happen,then Use Inet function to assign Port