I am not new to java but never done socket programming before. I was reading about reading a file from remote host is possible with URL but couldn't find if it is possible for client to update the file back to the server(Remote host not the local host)?
Can anyone please make me understand this. And if not possible then why?
You can certainly upload (not "update") a file to a web server, provided that the server provides a page which supports that. When you say it "can accept binary content" it sounds to me like there is a page which supports uploads.
You can write your own Java code for doing file uploads, but you have to learn a whole lot of boring details about the HTTP specifications. But it's really better to use Apache's HttpClient package -- you don't have to learn the boring specs and it works already.