Develop Reference

Chat server client sometimes cannot see message from other clients on the same server

I am making 2 classes for Chat server client for a project I am working on. The problem is server can see the message that sent to it(from client) and it can send those messages out to every clients BUT each client has to type in some input first if he wants to see the message from other users. I have no clue what I did wrong. Please help me out. Thanks in advance :)
Server Class
import java.net.*;
import java.util.ArrayList;
import java.io.*;
public class TestServer extends Thread
{
protected Socket clientSocket;
public static ArrayList<Socket> ConnectionArray = new ArrayList<Socket>();
public static ArrayList<String> CurrentUsers = new ArrayList<String>();
final static int PORT = 22;
public static void main(String[] args) throws IOException
{
ServerSocket serverSocket = null;
try
{
serverSocket = new ServerSocket(PORT);
System.out.println ("Connection Socket Created");
try
{
while (true)
{
System.out.println ("Waiting for Connection");
Socket sock = serverSocket.accept();
ConnectionArray.add(sock);
System.out.println("Client connected from: " + sock.getLocalAddress().getHostName());
new TestServer (sock);
}
}
catch (IOException e)
{
System.err.println("Accept failed.");
System.exit(1);
}
}
catch (IOException e)
{
System.err.println("Could not listen on port: " + PORT);
System.exit(1);
}
finally
{
try {
serverSocket.close();
}
catch (IOException e)
{
System.err.println("Could not close port: 10008.");
System.exit(1);
}
}
}
private TestServer (Socket inSock)
{
clientSocket = inSock;
start();
}
public void run()
{
System.out.println ("New Communication Thread Started");
//System.out.println ("Client connected from: " + sock.getLocalAddress().getHostName());
try {
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(),true);
BufferedReader in = new BufferedReader(new InputStreamReader( clientSocket.getInputStream()));
String inputLine;
while (true)
{
inputLine = in.readLine();
System.out.println ("Server: " + inputLine);
for(int i = 1; i <= TestServer.ConnectionArray.size(); i++)
{
System.out.println("Total Connection: " + ConnectionArray.size());
Socket TEMP_SOCK = (Socket) TestServer.ConnectionArray.get(i-1);
if (clientSocket != TEMP_SOCK)
{
PrintWriter TEMP_OUT = new PrintWriter(TEMP_SOCK.getOutputStream(), true);
TEMP_OUT.println(inputLine);
TEMP_OUT.flush();
System.out.println("Sending to: " + TEMP_SOCK.getLocalAddress().getHostName());
}
}
if (inputLine.equals("Bye."))
break;
}
out.close();
in.close();
clientSocket.close();
}
catch (IOException e)
{
System.err.println("Problem with Communication Server");
System.exit(1);
}
}
}
Client Class
import java.io.*;
import java.net.*;
public class TestClient {
public static void main(String[] args) throws IOException {
String serverHostname = new String ("127.0.0.1");
if (args.length > 0)
serverHostname = args[0];
System.out.println ("Attemping to connect to host " +
serverHostname);
Socket echoSocket = null;
PrintWriter out = null;
BufferedReader in = null;
try {
echoSocket = new Socket(serverHostname, 22);
out = new PrintWriter(echoSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(echoSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Don't know about host: " + serverHostname);
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for "
+ "the connection to: " + serverHostname);
System.exit(1);
}
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
String userInput;
System.out.println ("Type Message (\"Bye.\" to quit)");
while ((userInput = stdIn.readLine()) != null)
{
out.println(userInput);
if (userInput.equals("Bye."))
break;
System.out.println("Other user: " + in.readLine());
}
out.close();
in.close();
stdIn.close();
echoSocket.close();
}
}

You need a separate thread in the client for reading from the server without blocking on System.in;
Thread t = new Thread(() -> {
try {
while (!Thread.currentThread().isInterrupted()) {
System.out.println("Other user: " + in.readLine());
}
} catch (Exception e) {
e.printStackTrace();
}
});
t.start();
while ((userInput = stdIn.readLine()) != null)
{
out.println(userInput);
if (userInput.equals("Bye."))
break;
}
t.interrupt();

Server-client communication by using IP address doesn't work

Server application and client application are running in different computers. I want to send some message from client to server. The server should receive it and display. But in my case it's not happening. Nothing happens in server computer when something is sent.
This is my client program:
import java.io.*;
import java.net.*;
public class EchoClient {
//private static final String IP="194.47.46.36";
public EchoClient() {
}
public void establish() {
Socket echoSocket = null;
PrintWriter out = null;
BufferedReader in = null;
try {
//echoSocket = new Socket(InetAddress.getLocalHost(), 8080);
echoSocket = new Socket("195.47.46.76", 4444);
out = new PrintWriter(echoSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(
echoSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Don't know about host.");
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O");
System.exit(1);
}
BufferedReader stdIn = new BufferedReader(
new InputStreamReader(System.in));
String userInput;
try {
while ((userInput = stdIn.readLine()) != null) {
out.println(userInput);
if (userInput.equals("Bye."))
break;
System.out.println("echo: " + in.readLine());
}
out.close();
in.close();
stdIn.close();
echoSocket.close();
} catch (IOException ioe) {
System.out.println("Failed");
System.exit(
-1);
}
}
}

Server, Client socket implementation

Am writing a Server, client chat program using Java Socket. Here is my code for the Server socket class.
import java.io.*;
import java.net.*;
public class Main {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(8085);
} catch (IOException ex) {
System.out.println("IO Error, " + ex);
System.exit(1);
}
Socket clientSocket = null;
System.out.println("Listening for incoming connections");
try {
clientSocket = serverSocket.accept();
} catch (IOException ex) {
System.out.println("Failed to accept connection " + ex);
System.exit(1);
}
System.out.println("Connection Successful");
System.out.println("Listening to get input");
PrintStream output = new PrintStream(clientSocket.getOutputStream(), true);
BufferedReader input = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String inputLine;
while ((inputLine = input.readLine()) != null) {
System.out.println(inputLine);
System.out.println("Server: ");
inputLine = input.readLine();
output.println(inputLine);
if (!inputLine.equals("exit")) {
} else {
break;
}
}
output.close();
input.close();
clientSocket.close();
serverSocket.close();
}
}
The client is able to make a connection and send a message to the server. The server can also receive the messages sent by the client. The problem is that when the message is sent from the server, the client does not receive the message. Here is my client socket code.
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.Socket;
public class Client {
public static void main(String [] args) throws Exception
{
BufferedReader input;
PrintStream output;
BufferedReader clientInput;
try (Socket client = new Socket("127.0.0.1", 8085)) {
input = new BufferedReader(new InputStreamReader(client.getInputStream()));
output = new PrintStream(client.getOutputStream());
clientInput = new BufferedReader(new InputStreamReader(System.in));
String line;
while(true)
{
System.out.println("Client: ");
line = clientInput.readLine();
output.println("Server: " + line );
if(line.equals("quit"))
{
break;
}
}
}
input.close();
clientInput.close();
output.close();
}
}

Server side:
public class Server {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(8085);
} catch (IOException ex) {
System.out.println("IO Error, " + ex);
System.exit(1);
}
Socket clientSocket = null;
System.out.println("Listening for incoming connections");
try {
clientSocket = serverSocket.accept();
} catch (IOException ex) {
System.out.println("Failed to accept connection " + ex);
System.exit(1);
}
System.out.println("Connection Successful");
System.out.println("Listening to get input");
PrintStream output = new PrintStream(clientSocket.getOutputStream(), true);
BufferedReader input = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String inputLine;
while ((inputLine = input.readLine()) != null) {
System.out.println("Client request: " + inputLine);
String resp = "some response as you need";
output.println(resp);
System.out.println("Server response: " + resp);
if (!inputLine.equals("exit")) {
} else {
break;
}
}
output.close();
input.close();
clientSocket.close();
serverSocket.close();
}
}
Client side:
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.Socket;
public class Client {
public static void main(String[] args) throws Exception {
BufferedReader input;
PrintStream output;
BufferedReader clientInput;
try (Socket client = new Socket("127.0.0.1", 8085)) {
input = new BufferedReader(new InputStreamReader(client.getInputStream()));
output = new PrintStream(client.getOutputStream());
clientInput = new BufferedReader(new InputStreamReader(System.in));
while (true) {
String inputStr = clientInput.readLine();
output.println(inputStr);
System.out.println("Client: " + inputStr);
if (inputStr.equals("quit")) {
break;
}
String serverResp = input.readLine();
output.println("Server: " + serverResp);
}
}
}
}
It is tested.

It's always a good idea to flush your output streams when you are done with them, the info you are sending may have buffered.

The server is expecting an extra line from the client input here:
while ((inputLine = input.readLine()) != null) {
System.out.println(inputLine);
System.out.println("Server: ");
inputLine = input.readLine(); // <--- here
The client is not reading from the InputStream called input it gets when it connects to the server. It is only reading the local console input from clientInput.
In the while loop in Client.java you need something like this after the quit block to get the server's response:
System.out.println("Server: " + input.readLine());

iterative dictionary server in java

what it do..
1. an iterative dictionary server that is listening clients requests..
2. connection will be established..
3. server will accept input string from client..
4. then server will search meaning of string from a file..
5. then server will return meaning to the client..
problem is with the while loop of server.. if it finds word it will send that word's meaning to client..fine.. but if word is not found... this
if(d.equals(null)){
input="No knowledge";
out.println(input);
out.flush();
}
doesn't execute... client says null and server says null exception...
what i am doing wrong here... i'm not getting it...!!
i have tried to changed this code...
client-server online dictionary program in java
client:
import java.io.;
import java.net.;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Scanner;
public class DCC1 {
public static void main(String[] args) throws IOException {
final int PORT = 8888;
Socket s = null;
PrintWriter out = null;
try {
s = new Socket("localhost", PORT);
out = new PrintWriter(s.getOutputStream()); // Output stream to the server
}
catch (UnknownHostException ex) {
System.err.println("Unknown host: " + PORT);
System.err.println("Exception: " + ex.getMessage());
System.exit(1);
}
catch (IOException ex) {
System.err.println("Cannot get I/O for " + PORT);
System.err.println("Exception: " + ex.getMessage());
System.exit(1);
}
Scanner user = new Scanner(System.in); // Scanning for user input
System.out.print("Enter String: ");
String input;
input = user.next(); // Hold the input from the user
out.println(input); // Send it to the server
out.flush();
BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream( )));
System.out.println(br.readLine());
out.close();
s.close();
}
}
server:
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
public class DSC1
{
public static void main(String[] args) throws IOException
{
final int PORT = 8888;
final String FILE_NAME = "dictionary.dat";
ServerSocket server = new ServerSocket(PORT);
Socket s = null;
PrintWriter out = null;
Scanner in = null;
FileInputStream fin = null;
ObjectInputStream oin = null;
while (true)
{
try
{
s = server.accept();
}
catch (IOException ex)
{
System.err.println("Accept failed");
System.err.println("Exception: " + ex.getMessage());
System.exit(1);
}
System.out.println("Accepted connection from client");
try
{
in = new Scanner(s.getInputStream()); // Input stream from the client
out = new PrintWriter(s.getOutputStream()); // Output stream to the client
String temp = in.next(); // String holding the word sent from the client
System.out.println("From the client " + temp);
String input = null;
fin = new FileInputStream(FILE_NAME);// The dictionary file
oin = new ObjectInputStream(fin);
dictionary d = (dictionary)oin.readObject();
while(d!= null)
{
System.out.println("in loop...");
if(d.name.equals(temp)){
input=d.meaning;
d.printDic();
out.println(input);
out.flush();
break;
}
d = (dictionary)oin.readObject();
if(d.equals(null))
{
input="No knowledge";
out.println(input);
out.flush();
}
}
}
catch (ClassNotFoundException|IOException ex)
{
System.err.println("Exception: " + ex.getMessage());
System.out.println("Closing connection with client");
in.close();
System.exit(1);
}
in.close();
}
}
}

Don't use d.equals(null). If you want to check if d is null, just do if (d==null).
Why? There's no way this can return true, so probably that's the reason why this code never executes and you don't get what you expect.

Unable to get message from client in client-server program in java

I am writing a client-server program in java using TCP/IP. For the purpose, I wrote the following codes:
serversock.java:
import java.net.*;
import java.io.*;
public class serversock {
public static void main(String[] args) throws IOException
{
ServerSocket sersock = null;
try
{
sersock = new ServerSocket(10007);
}
catch (IOException e)
{
System.out.println("Can't listen to port 10007");
System.exit(1);
}
Socket clientSocket = null;
System.out.println("Waiting for connection....");
try
{
clientSocket = sersock.accept();
}
catch ( IOException ie)
{
System.out.println("Accept failed..");
System.exit(1);
}
System.out.println("Conncetion is established successfully..");
System.out.println("Waiting for input from client...");
PrintWriter output = new PrintWriter(clientSocket.getOutputStream());
BufferedReader input = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String inputLine = input.readLine();
while ( inputLine != null)
{
output.println(inputLine);
System.out.println("Server: " + inputLine);
inputLine = input.readLine();
}
input.close();
clientSocket.close();
sersock.close();
}
}
clientsock.java:
import java.util.*;
import java.io.*;
import java.net.*;
public class clientsock
{
public static void main(String[] args) throws IOException
{
Socket sock = new Socket("localhost",10007);
// Scanner scan = new Scanner(System.in);
PrintWriter output = new PrintWriter(sock.getOutputStream(),true);
BufferedReader input = new BufferedReader( new InputStreamReader(sock.getInputStream()));
String line = null;
BufferedReader stdInput = new BufferedReader( new InputStreamReader(System.in));
System.out.println("Enter data to send to server: ");
line = stdInput.readLine();
while ( (line) != "bye")
{
output.println(line.getBytes());
line = stdInput.readLine();
System.out.println("Server sends: " + input.read());
}
sock.close();
}
}
Now on running the programs I got the following output:
server:
shahjahan#shahjahan-AOD270:~/Documents/java$ java serversock
Waiting for connection....
Conncetion is established successfully..
Waiting for input from client...
Server: [B#4e25154f
shahjahan#shahjahan-AOD270:~/Documents/java$
client:
shahjahan#shahjahan-AOD270:~/Documents/java$ java clientsock
Enter data to send to server:
qwe
sdf
^Cshahjahan#shahjahan-AOD270:~/Documents/java$
The server is recieving different symbols, and client receives nothing. Please help me to solve it.

In the client replace:
output.println(line.getBytes());
with
output.println(line);