It is under 120 lines, uses Java SE API only, and the complexity is approximately the same. Go does have advantage of built-in selects and channels, which make parts of the logic nicer, but not by much IMO.
On the other hand, in Java almost no one uses standard library to write network apps like this. If I had to use external libraries, which would be the case in the majority of real-world projects, the implementation would look even better and clearer.
That's impressive. However, even the direct reimplementation has introduced a subtle bug - a connection that sends something other than "server" or "client" is left hanging and never closed (use nc with -N flag, and press Ctrl+D to send EOF to see what I mean - it should disconnect and yet it doesn't). While not a functional bug, it could still cause a DoS attack if someone wanted to hog all the available sockets.
In Go, this is avoided by `defer conn.Close()` which guarantees that the connection will be closed at the end of the function execution, no matter what. It's a sort-of nicer syntax of "try {} finally {}" that let's you write the cleanup code immediately after the setup code, instead of at the end.
> On the other hand, in Java almost no one uses standard library to write network apps like this
I'm curious about the way the average Java programmer would write such an application. Would you please write an example of such a program, using an external library that would make implementation both correct and easy to read?
It is under 120 lines, uses Java SE API only, and the complexity is approximately the same. Go does have advantage of built-in selects and channels, which make parts of the logic nicer, but not by much IMO.
On the other hand, in Java almost no one uses standard library to write network apps like this. If I had to use external libraries, which would be the case in the majority of real-world projects, the implementation would look even better and clearer.