I am running into some issues with the Java socket API. I am trying to display the number of players currently connected to my game. It is easy to determine when a player h
There is no TCP API that will tell you the current state of the connection. isConnected()
and isClosed()
tell you the current state of your socket. Not the same thing.
isConnected()
tells you whether you have connected this socket. You have, so it returns true.
isClosed()
tells you whether you have closed this socket. Until you have, it returns false.
If the peer has closed the connection in an orderly way
read()
returns -1readLine()
returns null
readXXX()
throws EOFException
for any other XXX.
A write will throw an IOException
: 'connection reset by peer', eventually, subject to buffering delays.
If the connection has dropped for any other reason, a write will throw an IOException
, eventually, as above, and a read may do the same thing.
If the peer is still connected but not using the connection, a read timeout can be used.
Contrary to what you may read elsewhere, ClosedChannelException
doesn't tell you this. [Neither does SocketException: socket closed.
] It only tells you that you closed the channel, and then continued to use it. In other words, a programming error on your part. It does not indicate a closed connection.
As a result of some experiments with Java 7 on Windows XP it also appears that if:
OP_READ
select()
returns a value of greater than zeroSelectionKey
is already invalid (key.isValid() == false
)it means the peer has reset the connection. However this may be peculiar to either the JRE version or platform.