Here I am sharing you a nice Client Server Authentication Application having one server that is communicating with multiple clients using TCP protocol as per your requirement.
Answer:
Here each client is connected in a separate thread from server and that thread contains all the information about the client. It will solve your concurrency problem.
See inline comments for more clarification.
Note: replace host name in LiveChatClient.java file before running this program at port no 1234
Steps to run the program:
- First run
LiveChatServer only for single time
- Then run
LiveChatClient for multiple clients as many as you want to add
Here is one more sample in the same context. Please have a look at Java Server with Multiclient communication.
Opcode.java:
Operation code that is used to set a client-server communication protocol
/**************** an interface to define different operation code **************/
public interface Opcode {
int CLIENT_USERNAME = 1;
int CLIENT_INVALID_USERNAME = 2;
int CLIENT_PASSWORD = 3;
int CLIENT_INVALID_PASSWORD = 4;
int CLIENT_CONNECTED = 5;
}
LiveChatServer.java:
Single server that is controlling multiple clients
/************************ Live Chat Server *******************/
import java.io.IOException;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashMap;
import java.util.LinkedHashMap;
public class LiveChatServer {
// Connection state info
private static LinkedHashMap<String, ClientThread> clientInfo = new LinkedHashMap<String, ClientThread>();
// TCP Components
private ServerSocket serverSocket;
// Main Constructor
public LiveChatServer() {
startServer();// start the server
}
public void startServer() {
String port = "1234";
try {
// in constractor we are passing port no, back log and bind address whick will be local
// host
// port no - the specified port, or 0 to use any free port.
// backlog - the maximum length of the queue. use default if it is equal or less than 0
// bindAddr - the local InetAddress the server will bind to
int portNo = Integer.valueOf(port);
serverSocket = new ServerSocket(portNo, 0, InetAddress.getLocalHost());
System.out.println(serverSocket);
System.out.println(serverSocket.getInetAddress().getHostName() + ":"
+ serverSocket.getLocalPort());
while (true) {
Socket socket = serverSocket.accept();
new ClientThread(socket);
}
} catch (IOException e) {
System.out.println("IO Exception:" + e);
System.exit(1);
} catch (NumberFormatException e) {
System.out.println("Number Format Exception:" + e);
System.exit(1);
}
}
public static HashMap<String, ClientThread> getClientInfo() {
return clientInfo;
}
// *********************************** Main Method ********************
public static void main(String args[]) {
new LiveChatServer();
}
}
LiveChatClient.java:
Multiple clients connected to single server
/************************ Live Chat Client *******************/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.SocketException;
public class LiveChatClient {
private String chatName;
private String password;
private String serverAddress;
// TCP Components
private Socket socket;
private BufferedReader in;
private PrintWriter out;
public LiveChatClient() {
initHostName();
runClient();// have fun
}
public void initHostName() {
try {
serverAddress = "<your system name>";
if (serverAddress == null)
System.exit(1);
serverAddress = serverAddress.trim();
if (serverAddress.length() == 0)// empty field
{
System.out.println("Server IP Address or Name can't be blank.");
initHostName();
return;
}
System.out.println("Trying to connect with server...\nServer IP Address:"
+ serverAddress);
// create socket
InetAddress inetAddress = InetAddress.getByName(serverAddress);
if (!inetAddress.isReachable(60000))// 60 sec
{
System.out
.println("Error! Unable to connect with server.\nServer IP Address may be wrong.");
System.exit(1);
}
initPortNo();
} catch (SocketException e) {
System.out.println("Socket Exception:\n" + e);
initHostName();
return;
} catch (IOException e) {
initHostName();
return;
}
}
public void initPortNo() {
try {
String portNo = "1234";
portNo = portNo.trim();
if (portNo.length() == 0)// empty field
{
System.out.println("Server port No can't be blank.");
initPortNo();
return;
}
System.out.println("Trying to connect with server...\nServer Port No:" + portNo);
socket = new Socket(serverAddress, 1234);
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out = new PrintWriter(socket.getOutputStream(), true);
} catch (IOException e) {
System.out.println("IO Exception:\n" + e);
initPortNo();
return;
}
}
public void sendChatName() throws IOException {
System.out.println("Enter user name:");
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String name = br.readLine();
if (name == null)
System.exit(1);
// title case (get only first 9 chars of chat name)
chatName = name.trim();
if (name.length() == 0) {
System.out.println("Please enter user name.");
sendChatName();
return;
}
// sending opcode first then sending chatName to the server
out.println(Opcode.CLIENT_USERNAME);
out.println(chatName);
}
public void sendPassword() throws IOException {
System.out.println("Enter password:");
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String name = br.readLine();
if (name == null)
System.exit(1);
// title case (get only first 9 chars of password)
password = name.trim();
if (name.length() == 0) {
System.out.println("Please enter password.");
sendPassword();
return;
}
// sending opcode first then sending password to the server
out.println(Opcode.CLIENT_PASSWORD);
out.println(password);
}
public void runClient() {
try {
sendChatName();
while (true) {
int opcode = Integer.parseInt(in.readLine());
switch (opcode) {
case Opcode.CLIENT_INVALID_USERNAME:
// this client is connecting
System.out.println(chatName + " is invalid user name. Try different one.");
sendChatName();
break;
case Opcode.CLIENT_PASSWORD:
sendPassword();
break;
case Opcode.CLIENT_INVALID_PASSWORD:
// this client is connecting
System.out.println(password + " is invalid password. Try different one.");
sendPassword();
break;
case Opcode.CLIENT_CONNECTED:
System.out.println(chatName + " is connected successfully.");
break;
}
}
} catch (IOException e) {
System.out.println("Client is closed...");
}
}
// *********************************** Main Method ********************
public static void main(String args[]) {
new LiveChatClient();
}
}
ClientThread.java:
Multiple thread started by server one for each client and containing information about all connected clients
/************************ Client Thread *******************/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.HashMap;
import java.util.Map;
public class ClientThread implements Runnable {
// TCP Components
private Socket socket;
private BufferedReader in;
private PrintWriter out;
private String chatName;
private String password;
// seperate thread
private Thread thread;
// boolean variable to check that client is running or not
private volatile boolean isRunning = true;
// opcode
private int opcode;
private static Map<String, String> userpass = new HashMap<String, String>();
static {
userpass.put("amit", "pass");
userpass.put("ajay", "word");
}
public ClientThread(Socket socket) {
try {
this.socket = socket;
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out = new PrintWriter(socket.getOutputStream(), true);
thread = new Thread(this);
thread.start();
} catch (IOException e) {
System.out.println(e);
}
}
public void run() {
try {
while (isRunning) {
if (!in.ready())
continue;
opcode = Integer.parseInt(in.readLine());// getting opcode first from client
switch (opcode) {
case Opcode.CLIENT_USERNAME:
chatName = in.readLine();
System.out.println(chatName + " is reqesting to connect.");
boolean result1 = userpass.containsKey(chatName);
if (result1) {
System.out.println(chatName + " is a valid username.");
out.println(Opcode.CLIENT_PASSWORD);
} else {
System.out.println(chatName + " is a invalid username.");
out.println(Opcode.CLIENT_INVALID_USERNAME);
}
break;
case Opcode.CLIENT_PASSWORD:
password = in.readLine();
System.out.println(chatName + " is reqesting to connect having password "
+ password);
boolean result2 = userpass.get(chatName).equals(password);
if (result2) {
System.out.println(password + " is a valid password for username "
+ chatName);
out.println(Opcode.CLIENT_CONNECTED);
} else {
System.out.println(password + " is a invalid password for username "
+ chatName);
out.println(Opcode.CLIENT_INVALID_PASSWORD);
}
break;
}
}
// close all connections
out.close();
in.close();
socket.close();
} catch (IOException e) {
System.out.println(e);
}
}
}
Here is the output when two client are added.
Server:
ServerSocket[addr=computerName/14.98.241.102,port=0,localport=1234]
computerName:1234
abc is reqesting to connect.
abc is a invalid username.
ajay is reqesting to connect.
ajay is a valid username.
ajay is reqesting to connect having password word
word is a valid password for username ajay
amit is reqesting to connect.
amit is a valid username.
amit is reqesting to connect having password word
word is a invalid password for username amit
amit is reqesting to connect having password pass
pass is a valid password for username amit
Client1:(ajay)
Trying to connect with server...
Server IP Address:computerName
Trying to connect with server...
Server Port No:1234
Enter user name:
abc
abc is invalid user name. Try different one.
Enter user name:
ajay
Enter password:
word
ajay is connected successfully.
Client2:(amit)
Trying to connect with server...
Server IP Address:computerName
Trying to connect with server...
Server Port No:1234
Enter user name:
amit
Enter password:
word
word is invalid password. Try different one.
Enter password:
pass
amit is connected successfully.
Use this program as initial starter for your application. Please let me know if you want to add new functionality in the program.
