java.net.SocketException: Connection reset

Question

There are several possible causes.

1. The other end has deliberately reset the connection, in a way which I will not document here. It is rare, and generally incorrect, for application software to do this, but it is not unknown for commercial software.

2. More commonly, it is caused by writing to a connection that the other end has already closed normally. In other words an application protocol error.

3. It can also be caused by closing a socket when there is unread data in the socket receive buffer.

4. In Windows, 'software caused connection abort', which is not the same as 'connection reset', is caused by network problems sending from your end. There's a Microsoft knowledge base article about this.

Connection reset simply means that a TCP RST was received. This happens when your peer receives data that it can't process, and there can be various reasons for that.

The simplest is when you close the socket, and then write more data on the output stream. By closing the socket, you told your peer that you are done talking, and it can forget about your connection. When you send more data on that stream anyway, the peer rejects it with an RST to let you know it isn't listening.

In other cases, an intervening firewall or even the remote host itself might "forget" about your TCP connection. This could happen if you don't send any data for a long time (2 hours is a common time-out), or because the peer was rebooted and lost its information about active connections. Sending data on one of these defunct connections will cause a RST too.

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Update in response to additional information:

Take a close look at your handling of the SocketTimeoutException. This exception is raised if the configured timeout is exceeded while blocked on a socket operation. The state of the socket itself is not changed when this exception is thrown, but if your exception handler closes the socket, and then tries to write to it, you'll be in a connection reset condition. setSoTimeout() is meant to give you a clean way to break out of a read() operation that might otherwise block forever, without doing dirty things like closing the socket from another thread.

Whenever I have had odd issues like this, I usually sit down with a tool like WireShark and look at the raw data being passed back and forth. You might be surprised where things are being disconnected, and you are only being notified when you try and read.

You should inspect full trace very carefully,

I've a server socket application and fixed a java.net.SocketException: Connection reset case.

In my case it happens while reading from a clientSocket Socket object which is closed its connection because of some reason. (Network lost,firewall or application crash or intended close)

Actually I was re-establishing connection when I got an error while reading from this Socket object.

Socket clientSocket = ServerSocket.accept();
is = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
int readed = is.read(); // WHERE ERROR STARTS !!!

The interesting thing is for my JAVA Socket if a client connects to my ServerSocket and close its connection without sending anything is.read() is being called repeatedly.It seems because of being in an infinite while loop for reading from this socket you try to read from a closed connection. If you use something like below for read operation;

while(true)
{
  Receive();
}

Then you get a stackTrace something like below on and on

java.net.SocketException: Socket is closed
    at java.net.ServerSocket.accept(ServerSocket.java:494)

What I did is just closing ServerSocket and renewing my connection and waiting for further incoming client connections

String Receive() throws Exception
{
try {                   
            int readed = is.read();
           ....
}catch(Exception e)
{
        tryReConnect();
        logit(); //etc
}


//...
}

This reestablises my connection for unknown client socket losts

private void tryReConnect()
        {
            try
            {
                ServerSocket.close();
                //empty my old lost connection and let it get by garbage col. immediately 
                clientSocket=null;
                System.gc();
                //Wait a new client Socket connection and address this to my local variable
                clientSocket= ServerSocket.accept(); // Waiting for another Connection
                System.out.println("Connection established...");
            }catch (Exception e) {
                String message="ReConnect not successful "+e.getMessage();
                logit();//etc...
            }
        }

I couldn't find another way because as you see from below image you can't understand whether connection is lost or not without a try and catch ,because everything seems right . I got this snapshot while I was getting Connection reset continuously.