UDP socket client / server

[Gunner 1]

Hello
I just started network programming in java, and I took my first sockets (client / server) via a UDP protocol. But that does not work. So, may be you can help me out, here is my code.

Public class serveurUDP {
	
	static int sz = 1024;
	static byte[] buff = new byte[sz];
	static int pt = 9332;
 
	Public static void hand(String[] args)throws Exception {
		DatagramSocket sc = new DatagramSocket(pt);
String give = "";
String message = "";
sz = 0;
System.out.System.out.println("Server Initialized");
		while(true) {
		DatagramPacket packet = new DatagramPacket(stamp, stamp.length);
sc.receive(Package);
System.out.System.out.println(package received from:+ Package.getAddress());
sz = packet.getLength();
gives = new String(package.getData(),0, Size);
message = "hello"+ yields;
System.out.System.out.println("Data that will be sent are:+ Message);
DatagramPacket send = new DatagramPacket(message.getBytes(), Message.length(), Pack.getAddress(), Pack.getPort());
sc.Send(sends);
		}
 
	}
 
}

[Linux-Us]

Hi,
As you except the announcement, the port is already used. In effect, you create a DatagramSocket in the hand of your customer with this port, but also in the hand of your server. Since you're on the same PC, it throws an exception. Your client does not need a port to create its socket. That's what you'll specify the DatagramPacket which will make it will contact the server as it is (it however you need to know the listening port of your server).

[Gunner 1]

Hey,
Thanks for the advice, as you said I have updated my code, please check and if I am wrong somewhere then guide me.

Public class TestInetAddress {

	Public static void hand(String[] args) throws IOException {
		ServerSocket ser = new ServerSocket(300);
Socket cl = ser.accept();
BufferedReader rd = new BufferedReader(new InputStreamReader(customer
.getInputStream()));
String line;

		try {
			while ((line = rd.readLine()) != null) {
				System.out.System.out.println(row);
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			rd.close();
customer.close();
ser.close();
 
		}
 
	}
 }

[SoftWore]

Hi,
- The connected mode (similar to a telephone), using TCP. In this mode of communication, a stable connection is established between the two processes, so that the destination address is not required for each submission of data.
- The non-connected mode (similar to a communication by mail), using the UDP protocol. This mode requires the destination address for each mailing, and no acknowledgment is given.

[Gunner 1]

Hello,
Level TCP or UDP is a little blurry but it's better. Otherwise thank you for the buffer I see what it is. For class server, I had not realized that this was only the server. Finally you've responded really well, thank you. (I found all of the same UDP is simpler than TCP, even though I know it is less reliable but faster)

BufferedWriter wr = new BufferedWriter(new OutputStreamWriter(customer.getOutputStream()));

But after, when I made
wr.Write (message.getBytes ())
but it is not working. So, is there any other method to send data over client and sever program.

[HardWeaR]

Hello,
You must give the ip of your server to people who want to connect, or when you have a domain name (DNS => basically a name associated with ip). Knowing that the ip is good, but not enough to connect to a server, the client must also know what port to connect (and with what protocol, TCP or UDP). From there the customer will use an InetSocketAddress (which contains an InetAddress).