Each client is registered as an observer once it connected to the server. When any client did changes, another clients would be notified.
My problem is how could I keep the socket connected?
Can I store all connections like Socket[] and check their InputStream every second?
I don't know if i got your problem right... But I'll give it a shot.
The Problem sems to be, that you have 1 ServerSocket and multiple sockets (one for each client) and now you want to get notified/informed about acitvity on these sockets. so you plan on iterating through the list of sockets?
The keyword is nonblocking I/O. Search for the Keyword "selector" or "multiplexing". I'll try to put up a simple example.
I build a really minimal example. But it is a start. This is the whole
package server;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.channels.spi.SelectorProvider;
import java.util.Iterator;
import java.util.Set;
public class Server {
public Server() throws IOException{
Selector selector = SelectorProvider.provider().openSelector();
ServerSocketChannel ssc = ServerSocketChannel.open().bind(new InetSocketAddress(9000));
ssc.configureBlocking(false);
ssc.register(selector,
SelectionKey.OP_ACCEPT);
while(true) {
int readyChannels = selector.select();
if(readyChannels == 0) continue;
Set<SelectionKey> selectedKeys = selector.selectedKeys();
Iterator<SelectionKey> keyIterator = selectedKeys.iterator();
while(keyIterator.hasNext()) {
SelectionKey key = keyIterator.next();
if(key.isAcceptable()) {
System.out.println("acceptable");
SocketChannel socketChan = ((ServerSocketChannel)key.channel()).accept();
socketChan.configureBlocking(false);
socketChan.register(selector, SelectionKey.OP_READ);
} else if (key.isConnectable()) {
// a connection was established with a remote server.
} else if (key.isReadable()) {
System.out.println("Processing reading...");
ByteBuffer buf = ByteBuffer.allocate(1024);
int readedBytes = ((SocketChannel)key.channel()).read(buf);
System.out.println("Readed: " + readedBytes);
buf.flip();
for(byte b : buf.array()) {
System.out.print((char) b);
}
} else if (key.isWritable()) {
// a channel is ready for writing
}
keyIterator.remove();
}
}
}
public static void main(String[] args) throws IOException {
Server server = new Server();
}
}
I can run this, and connect via netcat on port 9000 to it, and send messages from there. Just ONE Thread, with as many client connections as you like....
I used this ressources/examples
http://tutorials.jenkov.com/java-multithreaded-servers/thread-pooled-server.html and http://docs.oracle.com/javase/7/docs/technotes/guides/io/example/index.html
