Question

1. Two computers are connected by socket connection. If the server/client closes the connection
   from their end(i.e closes the InputStream, OutputStream and Socket) then how can I inform
   the other end about the disconnection? There is one way I know of – trying to read from the InputStream,
   which throws an IOException if connection is closed, but is there any other way to detect this?
2. Another question, I looked the problem up on the internet and saw inputStream.available()
   does not solve this problem. Why is that?

Additional Information : I’m asking for another way because my project becomes tough to handle if I have to try to read from the
InputStrem to detect a disconnection.

Answer 1

trying to read from the InputStream, which throws an IOException

That is not correct. If the peer closes the socket:

• read() returns -1
• readLine() returns null
• readXXX() throws EOFException, for any other X.

As InputStream only has read() methods, it only returns -1: it doesn’t throw an IOException at EOS.

Contrary to other answers here, there is no TCP API or Socket method that will tell you whether the peer has closed the connection. You have to try a read or a write.

You should use a read timeout.

InputStream.available() doesn’t solve the problem because it doesn’t return an EOS indication of any kind. There are few correct uses of it, and this isn’t one of them.