Java Socket doesn't unblock even with read timeout

Question

I have an application to write the request data over socket and read the response.

Some times Host doesn't respond to request and my code blocks, even though I'm using a read timeout.

There is no way to clear it manually and it require system to be rebooted or restart on the server handler required.

Here is the code used. Connection appears to block at objBufferedInputStream.read(..)

Socket clientSocket = new Socket(objInetAddress, hostPort);
clientSocket.setKeepAlive(true);
clientSocket.setReceiveBufferSize(8192);
clientSocket.setSendBufferSize(8192);
clientSocket.setSoTimeout(waitTimeBeforeSocketClose * 1000);
objBufferedInputStream = new BufferedInputStream(clientSocket
                    .getInputStream());
.......
objBufferedOutputStream.write(message, 0, message.length);
objBufferedOutputStream.flush();

while (bytesLeft > 0 && bytesread > -1) {
        try {
            bytesread = objBufferedInputStream.read(data, 4096 - bytesLeft, 1);             
        } catch (IOException e) {
            objLogger.writeException(e);
            try {
                objBufferedInputStream.close();
            } catch (IOException e1) {
                objLogger.writeException(e1);

                return null;
            }
            return null;
        }
        bytesLeft -= bytesread;
    }
    return data;

}

Please advise whether this is expected behavior when the host doesn't respond or hold the response.

Please advise whether there is alternate approach.

please read stackoverflow.com/help/how-to-ask and stackoverflow.com/help/mcve — specializt
– specializt, Commented Feb 17, 2015 at 15:47
XY problem. "Please advise whether this is expected behavior when the host doesn't respond or hold the response" and "please advise whether there is [an] alternate approach" both assume your code is correct. It isn't. — user207421
– user207421, Commented Feb 17, 2015 at 16:27

user207421 · Accepted Answer · 2015-02-18 12:58:48Z

1

Either:

waitTimeBeforeSocketClose is zero, so you are blocking indefinitely, or
It is non-zero, so you're getting a SocketTimeoutException inside your loop, and ignoring it, so you spin forever. Add a separate catch block for SocketTimeoutException with a break; inside it. Never just ignore an IOException. In this case I would say you should exit the loop on any IOException, so you could also consider putting the try/catch outside the loop.

Reading one byte at a time is pretty poor. I don't see the point of that.

edited Feb 18, 2015 at 12:58

answered Feb 17, 2015 at 16:11

user207421

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4 Comments

user2025698 Over a year ago

Hi, Thanks. I have updated the source code in the original post. We exit the loop when there is IOException. There is no exception thrown. I have even added logging before read method and it is printed only once and then there is no more action. This socket read/write happens with AS400 system to perform transactions.

user207421 Over a year ago

So what exactly is the value of waitTimeBeforeSocketClose?

user2025698 Over a year ago

It is set to 30 and application multiplies it by 1000 to make it 30 seconds.

user2025698 Over a year ago

I have made the changes to use read available to fix this issue. Please advise whether available is fine instead of specifying the number of bytes. this change make it faster as it read all the values in two to three iterations objBufferedInputStream.read(data, 4096 - bytesLeft, objBufferedInputStream.available)

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