Echo Server/Client

1. Echo Server

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import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket;   public class EchoServer {       public static void main(String[] args) throws IOException {         int portNumber = 30000;           ServerSocket serverSocket = new ServerSocket(portNumber);         Socket socket = serverSocket.accept();         PrintWriter out = new PrintWriter(socket.getOutputStream(), true);         BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));           String echo;         while ((echo = in.readLine()) != null) {             System.out.println("echo: " + echo);             out.println(echo);             out.flush();         }                   in.close();         out.close();         socket.close();         serverSocket.close();     } }

2. Echo Client

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import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; import java.net.Socket; import java.net.UnknownHostException;   public class EchoClient {       public static void main(String[] args) throws UnknownHostException, IOException {         String hostName = "127.0.0.1";         int portNumber = 30000;           Socket socket = new Socket(hostName, portNumber);         PrintWriter out = new PrintWriter(socket.getOutputStream(), true);         BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));         BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));           String userInput;         while ((userInput = stdIn.readLine()) != null) {             out.println(userInput);             out.flush();             System.out.println("echo: " + in.readLine());         }           in.close();         out.close();         socket.close();     } }