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How do i establish communication between socket threads of server in order to communicate between clients?

so i'm trying to create a chess server for a chess application i wrote in java. The two classes i'm including are the main class that starts my TCPServerThreads and this class itselve.
I am able to connect two clients and for example echo their input back to them, but i have no idea, how to exchange information between these two threads. I am trying to forward Server inputs from one client towards the main class, or directly to the other client, so i can update the chess field on the client.
It's pretty much my first time working with servers, so thanks in advance for you patience.
This is my main class:
package Main;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import TCP.TCPServerThread;
public class Main {
public static final String StopCode = "STOP";
public static final int PORT = 8888;
public static int count = 0;
public static void main(String[] args) {
ServerSocket serverSocket = null;
Socket socket = null;
//create Server Socket
try {
serverSocket = new ServerSocket(PORT);
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("serverSocket created");
//accept client Sockets
while (count < 2) {
try {
socket = serverSocket.accept();
count ++;
System.out.println("socket Nr " + count + " accepted");
} catch (IOException e) {
System.out.println("I/O error: " + e);
}
// new thread for a client
new TCPServerThread(socket).start();
}
}
}
And this is the TCPServerThread:
package TCP;
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;
import java.sql.Timestamp;
import Main.Main;
public class TCPServerThread extends Thread{
Timestamp ts;
private int port = 0;
Socket socket;
public TCPServerThread(Socket clientSocket) {
this.socket = clientSocket;
}
public void run() {
InputStream is = null;
BufferedReader br = null;
DataOutputStream os = null;
try {
is = socket.getInputStream();
br = new BufferedReader(new InputStreamReader(is));
os = new DataOutputStream(socket.getOutputStream());
} catch (IOException e) {
return;
}
String line;
while (true) {
try {
line = br.readLine();
if ((line == null) || line.equalsIgnoreCase("QUIT")) {
socket.close();
return;
} else {
if(line.equalsIgnoreCase("sp") && this.activeCount() == 3) {
os.writeBytes("1" + "\n\r");
os.flush();
}
os.writeBytes("Echo reply: " + line + "\n\r");
os.flush();
}
} catch (IOException e) {
e.printStackTrace();
return;
}
}
}
}

Thank you very much! I made the tcp threads implement runnable instead of extend thread. Then i added a ConnectionManager between the main and the TCPThreads which isn't static. This way i can put the manager into the TCPThreads constructor and communicate between its objects.

Handle java.net.SocketException: Socket closed when multithreading?

I'm doing a school project where we are supposed to create a simplefied Hotel booking system and then use it with a server/client communication.
Since I wanted to push the project a bit and do a multithreaded program, I've got a Socket Exception that I'm not sure how to handle. I've searched everywhere for an answer and I know that the exception occours because I'm trying to use a socket that has been closed. But from what I've read on Oracle-docs, their example is doing that as well.
So, is this actually Ok, just that I need to handle the exception? Cause my code runs fine, I just see the exceptions since I've put e.printStackTrace(); in my catch.
My Client class:
package client;
import java.io.*;
import java.net.Socket;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.Scanner;
public class Client {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
try {
Socket client = new Socket("localhost", 6066);
//System.out.println("Just connected to " + client.getRemoteSocketAddress());
OutputStream outToServer = client.getOutputStream();
DataOutputStream out = new DataOutputStream(outToServer);
InputStream inFromServer = client.getInputStream();
DataInputStream in = new DataInputStream(inFromServer);
LocalDate localDate = LocalDate.now();
String date = DateTimeFormatter.ofPattern("yyy/MM/dd").format(localDate);
System.out.println(in.readUTF());
System.out.print("Namn: ");
String name = sc.nextLine();
System.out.print("Ålder: ");
String age = sc.nextLine();
out.writeUTF(name);
out.writeUTF(age);
out.writeUTF(date);
System.out.println(in.readUTF());
client.close();
}catch(IOException e) {
e.printStackTrace();
}
}
}
And my Server class:
package server;
import java.io.IOException;
import java.net.*;
public class Server {
public static void main(String [] args) throws IOException {
int port = 6066;
ServerSocket server = new ServerSocket(port);
while(true) {
System.out.println("Listening for client..");
try {
Socket connectedClient = server.accept();
ClientHandle ch = new ClientHandle(connectedClient);
Thread t = new Thread((Runnable) ch);
t.start();
}catch (IOException e) {
}
}
}
}
And then my ClientHandle class which has the run() for the server-side:
package server;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.net.*;
import resources.*;
public class ClientHandle implements Runnable{
Socket connectedClient;
DataInputStream in;
DataOutputStream out;
public ClientHandle(Socket connectedClient) {
this.connectedClient = connectedClient;
try{
this.in = new DataInputStream(this.connectedClient.getInputStream());
this.out = new DataOutputStream(this.connectedClient.getOutputStream());
}catch(IOException ex) {
}
}
Hotel hotel = new Hotel();
Ticket yourTicket = new Ticket();
Server server = new Server();
#Override
public void run() {
while (true) {
try {
InetAddress host = InetAddress.getLocalHost();
System.out.println("Client " + host + " has connected.");
out.writeUTF("Välkommen till Hotel Gisslevik!\nVänligen fyll i nedan information för att slutföra din bokning.\n");
String yourName = in.readUTF();
String age = in.readUTF();
int yourAge = Integer.parseInt(age);
String date = in.readUTF();
yourTicket.setDate(date);
Person guest = new Person(yourName, yourAge);
hotel.setRooms();
Integer room = hotel.getRoom();
String rent = "J";
if (rent.indexOf("J") >= 0) {
yourTicket.setId(yourName);
if (hotel.checkIn(guest, room, yourTicket.getId(), yourTicket.getDate())) {
String yourId = yourTicket.getId();
out.writeUTF("\nDitt rum är nu bokat den " + date + ". \nBokningsnummer: " + yourId);
}
}
out.flush();
connectedClient.close();
}catch (EOFException e) {
} catch (IOException e) {
e.printStackTrace();
break;
}
}
}
}
If I just comment e.printStackTrace(); the exceptions doesn't show, but I would like to know how to handle them (if they should be handled). I've been searching the internet for days and checked out tutorials, but I don't find a proper answer to this.
I really appreciate any help you can provide.

Handle java.net.SocketException: Socket closed
Don't close the socket and then continue to use it.
when multithreading?
Irrelevant.
You have connectedClient.close() inside your while (true) loop. Solution: move it outside.

Java Server, Unity C# Client Are Freezing

I am building a Sphinx4 Java Server where Unity3D should communicate with. Sending audio data from Unity C# to the Java server works fine. Speech recognition with the received data works fine too. The problem appears when I try to send data from Java back to C#.
My current code:
JAVA
package main;
import java.io.InputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import edu.cmu.sphinx.api.Configuration;
import edu.cmu.sphinx.api.SpeechResult;
import edu.cmu.sphinx.api.StreamSpeechRecognizer;
public class SpeechRecognition {
private static StreamSpeechRecognizer recognizer;
private static Configuration configuration;
public static void main(String[] args) {
configuration = new Configuration();
configuration.setAcousticModelPath("resource:/edu/cmu/sphinx/models/en-us/en-us");
configuration.setDictionaryPath("resource:/edu/cmu/sphinx/models/en-us/cmudict-en-us.dict");
configuration.setLanguageModelPath("resource:/edu/cmu/sphinx/models/en-us/en-us.lm.bin");
try {
recognizer = new StreamSpeechRecognizer(configuration);
ServerSocket serverSocket = new ServerSocket(82);
while (System.in.available() == 0) {
Socket socket = serverSocket.accept();
System.out.println("Client found");
String recognized = RecognizeText(socket.getInputStream());
System.out.println("sending now");
PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
String json = recognized;
out.print(json);
out.flush();
out.close();
socket.close();
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Quitting...");
serverSocket.close();
}
private static String RecognizeText(InputStream stream) throws Exception {
recognizer.startRecognition(stream);
SpeechResult result;
String resultString="";
while ((result = recognizer.getResult()) != null) {
resultString = result.getHypothesis();
System.out.format("Hypothesis: %s\n", resultString);
}
recognizer.stopRecognition();
return resultString;
}
}
Now my C# code is like this:
void Start () {
dataPath = Application.dataPath;
t = new Thread(Client);
t.Start();
}
private void Client()
{
String input;
TcpClient tcpClient = new TcpClient("localhost", 82);
NetworkStream networkStream = tcpClient.GetStream();
BinaryWriter bw = new BinaryWriter(networkStream);
var filepath = dataPath + "/Resources/audio/test.wav";
FileStream filestream = new FileStream(filepath, FileMode.Open, FileAccess.Read);
BinaryReader filereader = new BinaryReader(filestream);
byte[] bytes = filereader.ReadBytes((Int32)filestream.Length);
bw.Write(bytes);
bw.Flush();
StreamReader streamReader = new StreamReader(networkStream);
input = streamReader.ReadToEnd();
print("Received data: " + input + "\n");
}
The recognition takes around 10 seconds. When te result is given the system freezes.
The Println("sending now") (in Java) is not printed. So it freezes before it even reaches it.
The weird thing is: When I only send text from Java to C# or from C# to Java, it works. If I want to send and receive on both ends, it freezes. And I need to send and receive data at the same time

I have found the anwser:
The loop is not broken in RecognizeText, placing the return statement within the while loop fixes the issue, as the recognized text will be returned first anyway.

Java gui, Client issue when trying to convert into gui

I have made a Client/Server programme in java, I have gotten it to work using the cmd perfectly as i want, now i am trying to convert the client side of the code into GUI, however i am having trouble with printing the client msg and reading the client input from the text fields and the server msg, here is what I have done so far, i get no errors when compiling but the gui it self doesn't run, any help is appreciated.
Here is the Client code:
import java.net.*;
import java.io.*;
import java.awt.*;
import java.util.Scanner;
import javax.swing.*;
public class TcpClient
{
public static void main(String[] args)
{
try
{
new TcpClient().start();
}
catch(Exception e)
{
System.out.println("Major Error" + e.getMessage());
e.printStackTrace();
}
}
public void start() throws IOException
{
JFrame build = new JFrame("Client");
JTextField serv = new JTextField();
JTextField clie = new JTextField();
build.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
serv.setBounds(50,210,300,50);
build.add(serv);
clie.setBounds(350,210,300,50);
build.add(clie);
//=====================================================================
Socket clientSocket = null;
InetAddress hostA = null;
PrintWriter clientOutput = null;
BufferedReader clientInput = null;
BufferedReader standardInput = null;
try
{
hostA = InetAddress.getLocalHost();
clientSocket = new Socket(hostA.getHostName(), 5600);
clientInput = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
clientOutput = new PrintWriter(clientSocket.getOutputStream(), true);
standardInput = new BufferedReader(new InputStreamReader(System.in));
String serverMsg, clientMsg;
//read from a socket and respond back to server
while((serverMsg = clientInput.readLine()) != null)
{
serv.setText("Server Saying - " + serverMsg);
if(serverMsg.equals("exit"))
break;
clientMsg = standardInput.readLine();
if(clientMsg != null)
{
clie.setText("Client Saying - " + clientMsg);
clientOutput.println(clientMsg);
}
}
}
catch(UnknownHostException e)
{
System.exit(1);
}
catch(IOException e)
{
System.exit(1);
}
finally
{
//clean up time
clientOutput.close();
clientInput.close();
standardInput.close();
clientSocket.close();
}
//=====================================================================
build.setLayout(null);
build.setSize(700,600);
build.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
build.setVisible(true);
build.setResizable(false);
}
}

As mentioned in the comments you should study multithreading and especially the EDT
What is happening right now is that your code and your GUI and preventing each other from working properly. By having your GUI run on the EDT your application can run without holding back the GUI. When the application has changes to report that are relevant for your GUI you can just inform the EDT when the time comes.

http server and client implementing head and get method

I'm trying to make a simple http client server using java. It will show the client's request as well as the server's response. For example server will send back
HTTP/1.0 200 OK
Connection: Close. etc.
Previously i had a echo client server. Now I've turned my echo server to act as a http server. I've tried Goggling about how to implement the head and get with the client but i noticed usually all of the example used apache framework. Is there a way to implement these method without apache framework.
My echo client which i'm trying to convert into a http client:
import java.io.*;
import java.net.*;
public class Ec1
{
public static void main(String[] args)
{
try
{
Socket s = new Socket("127.0.0.1", 80);
BufferedReader r = new BufferedReader(new InputStreamReader(s.getInputStream()));
PrintWriter w = new PrintWriter(s.getOutputStream(), true);
BufferedReader con = new BufferedReader(new InputStreamReader(System.in));
String line;
do
{
line = r.readLine();
if ( line != null )
System.out.println(line);
line = con.readLine();
w.println(line);
}
while ( !line.trim().equals("bye") );
}
catch (Exception err)
{
System.err.println(err);
}
}
}
My Http server:
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class Echo
{
protected void start() {
ServerSocket s;
System.out.println("Webserver starting up on port 80");
try {
// create the main server socket
s = new ServerSocket(80);
} catch (Exception e) {
System.out.println("Error: " + e);
return;
}
Socket clientSocket = null;
System.out.println ("Waiting for connection.....");
try {
clientSocket = s.accept();
System.out.println("Connection, sending data.");
BufferedReader in = new BufferedReader(new InputStreamReader(
clientSocket.getInputStream()));
PrintWriter out = new PrintWriter(clientSocket.getOutputStream());
String str = ".";
while (!str.equals(""))
str = in.readLine();
out.println("HTTP/1.0 200 OK");
out.println("Content-Type: text/html");
out.println("Server: Bot");
out.println("");
out.println("<H1>Welcome to the Ultra Mini-WebServer</H2>");
out.flush();
clientSocket.close();
s.close();
} catch (Exception e) {
System.out.println("Error: " + e);
}
}
public static void main(String args[]) {
WebServer ws = new WebServer();
ws.start();
}
}

Yes, there is, just interpret your request you're getting from the client.
From the following code (in HttpServer), parse:
String str = ".";
while (!str.equals("")) {
str = in.readLine();
if (str.startsWith("HEAD")) {
//Head execution here...
}
}
Etc...

Everybody uses some kind of library or framework for the client and/or the server side because HTTP is somewhat complex and there is no need to reinvent every wheel. However, it is quite possible to write your own implementation by starting directly from the RFCs for HTTP.