CODEWITHSUNDEEP
javanetwork-programmingudpclient-server
Deepak Kumar Gupta
Deepak Kumar Gupta

Reputation: 23

Udp Server Client java

I have written UDP server client program. The problem that i am facing is that when i am running server program, it is not waiting for client to connect. Whole code is executing after running till the end. And when i am running client side in between of execution of server side, client side is receiving data from its point of execution. Here is my server code-

public static void main(String args[]) throws Exception
  {
     DatagramSocket serverSocket = new DatagramSocket(4321);
        byte[] sendData;
        String sentence = null;
        FileInputStream file = new FileInputStream(new File("E:\\Deepak.txt"));
        InetAddress IPAddress=InetAddress.getByName("localhost");
        BufferedReader in = new BufferedReader(new InputStreamReader(file));
     do{
              while((sentence = in.readLine()) != null)
              {
              Thread.sleep(3000);
              System.out.println(sentence);
              sendData = sentence.getBytes();
              DatagramPacket sendPacket =new DatagramPacket(sendData, sendData.length,IPAddress,9876);
              serverSocket.send(sendPacket);
             }
           }while(true);
  }

Here is my client side code-

public static void main(String args[]) throws SocketException, UnknownHostException, IOException 
{
    DatagramSocket clientSocket = new DatagramSocket();
    byte[] receiveData = new byte[1024];
    String sentence ;
    while(true) 
           {                 
             DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
             receivePacket.getLength();
             System.out.println(receivePacket.getLength());
             clientSocket.receive(receivePacket);
             sentence = new String( receivePacket.getData());                  
           }
  }

Upvotes: 1

Views: 2010

Answers (1)

Krzysztof Krasoń
Krzysztof Krasoń

Reputation: 27466

UDP is connectionless, so there is no such thing as a connection in it. You can only send a packet (in a fire and forget way, send in java will send the data to the port specified in the Datagram) or receive packet on the port (receive in java will block until there is a packet received).

So you would need to implement your own connection on top of UDP if you want to have a server that only sends data if client "connects" to it.

So summing up:

  • send won't wait for anything, it will just throw the datagram on the wire
  • receive will wait for a datagram to arrive

Having the above information you would need to write your own protocol to keep the connection.

Upvotes: 1

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