Question

this is my Main class which belongs to the server application! but it is really surprizing that without running the client application,these sentences will be written in the console.would you please help me why?thanks.

my Main class:

public class Main {

static Socket client = null;
static ServerSocket server = null;

// We can have 10 clients' connections
static ClientThread t[] = new ClientThread[10];

public static void main(String args[]) {
    System.out.println("Server is starting...");
    System.out.println("Server is listening...");
    try {
        server = new ServerSocket(5050);
        System.out.println("Client Connected...");


        while (true) {

            client = server.accept();
            for (int i = 0; i <= 9; i++) {
                if (t[i] == null) {
                    (t[i] = new ClientThread(client, t)).start();
                    break;
                }
            }
        }
    } catch (IOException e) {
        System.out.println(e);
    }
}
}

// This client thread opens the input and the output streams for a particular client,
// ask the client's name, informs all the clients currently connected to the
// server about the fact that a new client has joined the chat room,
// and as long as it receive data, echos that data back to all other clients.
// When the client leaves the chat room this thread informs also all the
// clients about that and terminates.

class ClientThread extends Thread {

DataInputStream is = null;
PrintStream os = null;
Socket clientSocket = null;
ClientThread t[];

public ClientThread(Socket clientSocket, ClientThread[] t) {
    this.clientSocket = clientSocket;
    this.t = t;
}

@Override
public void run() {
    String line;
    String name;
    try {
        is = new DataInputStream(clientSocket.getInputStream());
        os = new PrintStream(clientSocket.getOutputStream());
        os.println("Enter your name.");
        name = is.readLine();
        os.println("Hello " + name + " to our chat room.\nTo leave enter /quit in a new line");
        for (int i = 0; i <= 9; i++) {
            if (t[i] != null && t[i] != this) {
                t[i].os.println("*** A new user " + name + " entered the chat room !!! ***");
            }
        }
        while (true) {
            line = is.readLine();
            if (line.startsWith("/quit")) {
                break;
            }
            for (int i = 0; i <= 9; i++) {
                if (t[i] != null) {
                    t[i].os.println("<" + name + "> " + line);
                }
            }
        }
        for (int i = 0; i <= 9; i++) {
            if (t[i] != null && t[i] != this) {
                t[i].os.println("*** The user " + name + " is leaving the chat room !!! ***");
            }
        }

        os.println("*** Bye " + name + " ***");

        // Clean up:
        // Set to null the current thread variable such that other client could
        // be accepted by the server

        for (int i = 0; i <= 9; i++) {
            if (t[i] == this) {
                t[i] = null;
            }
        }

        // close the output stream
        // close the input stream
        // close the socket

        is.close();
        os.close();
        clientSocket.close();
    } catch (IOException e) {
        System.out.println(e);
    }
}}

in the console:

init:
deps-jar:
compile-single:
run-single:
Server is starting...
Server is listening...
Client Connected...

Answer 1

you create a Socket and declare that the client is connected before accepting a connection :

        server = new ServerSocket(5050);
        System.out.println("Client Connected...");

you should print

client is connected

after this line

client = server.accept();

which blocks until a client actually connects