I'm just wondering if it is possible to use the SocketChannel class (with ByteBuffer) to simulate the blocking features of the regular Socket class in Java. I made two Test projects, one simulating the Client and the other simulating the Server:
Client Code:
public static void main(String[] args) throws IOException {
SocketChannel socket = SocketChannel.open(new InetSocketAddress("127.0.0.1", 6789));
//Simulate this:
//DataOutputStream dos = new DataOutputStream(socket.socket().getOutputStream());
//dos.writeInt(4);
//dos.writeInt(6);
ByteBuffer buffer = ByteBuffer.allocate(4);
buffer.putInt(4);
buffer.flip();
socket.write(buffer);
buffer.clear();
buffer.putInt(6);
buffer.flip();
socket.write(buffer);
}
Server Code:
public static void main(String[] args) throws IOException, InterruptedException {
ServerSocketChannel ssc = ServerSocketChannel.open();
ssc.socket().bind(new InetSocketAddress(6789));
SocketChannel socketCh = ssc.accept();
socketCh.configureBlocking(true);
// Simulate this
// DataInputStream dis = new DataInputStream(socketCh.socket().getInputStream());
// System.out.println(dis.readInt());
// System.out.println(dis.readInt());
// This is something to avoid. This is not the same as what is up above
// If the 2nd line prints -1, the 3rd prints 4
// If the 2nd line prints 4, the 3rd prints 6
ByteBuffer buffer = ByteBuffer.allocate(1024);
socketCh.read(buffer);
buffer.rewind();
System.out.println("First number: " + buffer.getInt());
buffer.clear();
System.out.println("Change: " + socketCh.read(buffer));
buffer.rewind();
System.out.println("Second Number: " + buffer.getInt());
}
As I said in the comments, the results of running the Server then the Client (in that order) are unpredictable, since sometimes the second number might remain as 4 or become 6, with the Change being -1 or 4(bytes in Integer) respectively.
As for the server side, I know I can make it wait so that the second socketCh.read(buffer) returns a value other than -1, which means nothing was written (I presume) in the SocketChannel.
However, on the client side, I don't have any ideas.
I am aware that I can instead use DataOutputStream and DataInputStream and do it the old fashioned way, but I want to know how to do it with SocketChannels simply for convenience. Also you can't go wrong with another trick up your sleeve.
Even though I manually configured the server as blocking, I assume it's the default configuration so it's ok to discard it.
Thank you in advance! PS: Hopefully I could avoid using the Selector classes for such a simple task...
EDIT: I know that the Selector classes can only be used for non-blocking mode.
