Why a "java.net.SocketException: Broken pipe" will occur?

Question

I wrote a simple socket programme, it works fine, but my friend use a port scanning tool, when it scan to the port I am using, it cash with "java.net.SocketException: Broken pipe" error, what's happen? and how to solve it?

providerSocket = new ServerSocket(portNum);
connection = providerSocket.accept();
if (connection.getOutputStream() != null) {
    //this line crash!!!
    out = new ObjectOutputStream(connection.getOutputStream());
    out.flush();

}

Detail Error from console:

java.net.SocketException: Broken pipe
    at java.net.SocketOutputStream.socketWrite0(Native Method)
    at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:92)
    at java.net.SocketOutputStream.write(SocketOutputStream.java:136)
    at java.io.ObjectOutputStream$BlockDataOutputStream.drain(ObjectOutputStream.java:1847)
    at java.io.ObjectOutputStream$BlockDataOutputStream.setBlockDataMode(ObjectOutputStream.java:1756)
    at java.io.ObjectOutputStream.<init>(ObjectOutputStream.java:230)

Answer 1

Some port scanners work by starting to open a connection and then immediately terminating it. Your server is not programmed to deal with a connection failure because you did not code for that possibility. You will need to use a try/catch to trap that condition and recover. Also, you should probably be handing off the connection to a separate thread for processing, so your main program can continue to receive new connections (and sending them to threads to be handled).

Answer 2

I think this happens when remote end closed the connection;