Read all byte from InputStream

Question

I want to asynchronously read all bytes from the InputStream of an active tcp connection. There could be nothing in the inputbuffer, in this case I want an empty byte array[] and NOT a read/timeout.

I tried this:

byte[] bytes = IOUtils.toByteArray(tcpInputStream);

But if there is nothing in the InputStream the read hangs until the tcp timeout and then an exception is thrown.

IOUtils is not in the standard library ... so what is it and does it offer an asynchronous version? — dsh, Jul 23 '15 at 16:21
If you only want to read the data that is *immediately* available, that's what the `available()` call is for. It's rarely useful though... — Jon Skeet, Jul 23 '15 at 16:22
@dsh: I assume it's apache commons-io. I don't have an answer to this, however, I have found two stackoverflow questions which may help you: http://stackoverflow.com/questions/19833068/async-commons-io-operations and http://stackoverflow.com/questions/5049319/how-to-create-a-java-non-blocking-inputstream-from-a-httpsurlconnection — beosign, Jul 23 '15 at 16:37

score 0 · Answer 1 · answered Jul 23 '15 at 19:08

You can use non blocking SocketChannels:

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;

...

SocketChannel socketChannel = SocketChannel.open();
socketChannel.connect(new InetSocketAddress("127.0.0.1", 80));
ByteBuffer buffer = ByteBuffer.allocate(2048);
int bytesRead;
while ((bytesRead = socketChannel.read(buffer)) >= 0) {
    if (bytesRead == 0)
        Thread.sleep(1000); // do usefull stuff
    else {
        // use the bytes and prepare the buffer for next read
        buffer.clear();
    }
}
socketChannel.close();

Also prepare for a IOException when the server closes the connection.

Read all byte from InputStream

1 Answers1