I have a socket client sending text to a socket server but the ReadLine doesnt seem to wait to receive a line before proceeding. Here is the of the server receiving the text:
public void run() {
try {
serveurSocket = new ServerSocket(PORT_ID);
connexionSocket = serveurSocket.accept();
BufferedReader reader = new BufferedReader(new InputStreamReader(connexionSocket.getInputStream()));
PrintWriter writer = new PrintWriter(connexionSocket.getOutputStream(), true);
messageRecu = "";
while (true) {
messageRecu = reader.readLine();
messageRecu = messageRecu.toUpperCase();
writer.println(messageRecu);
}
//reader.close();
//writer.close();
} catch (IOException e) {
System.out.println(e.getMessage());
e.printStackTrace();
}
}
After establishing the socket between client and server, the execution halts at reader.readLine until I send manually a string thru the socket. Which is normal and wanted. Codes resumes and its fine until its loops back to reader.ReadLine() where it will read a "null" line instead of waiting for input from the socket like it did the first time... this will obviously mess up the next command to uppercase. So how can I fix this?
EDIT: I'll add the client side if that can help understand.
public class ClientSocket {
private Socket clientSocket;
public boolean isClosed() { return clientSocket.isClosed(); }
public boolean connectToSocket (String ip, int port) {
try {
clientSocket = new Socket(ip, port);
return true;
}
catch (IOException e) {
System.out.println(e);
return false;
}
}
public String sendToServer(String messageClient) {
String messageRecu = "";
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
PrintWriter writer = new PrintWriter(clientSocket.getOutputStream(), true);
writer.println(messageClient);
messageRecu = reader.readLine();
reader.close();
writer.close();
return messageRecu;
}
catch (IOException e) {
System.out.println(e.getMessage());
e.printStackTrace();
return messageRecu;
}
}
}
A button press will call "connectTosocket" to initiate the socket. A second button when pressed will send the content of a textfield using "sendToServer".
Server does receive the message and return it capitalized but I wish for the socket to remain open with the server and if I send an other string for the same sequence to happen. Not even sure it can be done :(
According to the documentation of BufferedReader#readLine, a null is returned if the end of stream has been reached.
Change your reading loop to :
while ((messageRecu = reader.readLine()) != null) {
messageRecu = messageRecu.toUpperCase();
writer.println(messageRecu);
}
//Get out of the loop when the end of stream is reached.
As per Reading from and Writing to a Socket chapter of the Java tutorial.
As a side note, while(true) loops are not really appreciated.
The "null" signals for end of connection from the client side - which is why the connection disconnects. If you want to support multiple requests, you should run a new ServerSocket.accept() each time and wait for a new client to connect.
KKMultiServer class:
import java.net.*;
import java.io.*;
public class KKMultiServer {
public static void main(String[] args) throws IOException {
if (args.length != 1) {
System.err.println("Usage: java KKMultiServer <port number>");
System.exit(1);
}
int portNumber = Integer.parseInt(args[0]);
boolean listening = true;
try (ServerSocket serverSocket = new ServerSocket(portNumber)) {
while (listening) {
new KKMultiServerThread(serverSocket.accept()).start();
}
} catch (IOException e) {
System.err.println("Could not listen on port " + portNumber);
System.exit(-1);
}
}
}
KKMultiServerThread class:
import java.net.*;
import java.io.*;
public class KKMultiServerThread extends Thread {
private Socket socket = null;
public KKMultiServerThread(Socket socket) {
super("KKMultiServerThread");
this.socket = socket;
}
public void run() {
try (
PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(
socket.getInputStream()));
) {
String inputLine, outputLine;
KnockKnockProtocol kkp = new KnockKnockProtocol();
outputLine = kkp.processInput(null);
out.println(outputLine);
while ((inputLine = in.readLine()) != null) {
outputLine = kkp.processInput(inputLine);
out.println(outputLine);
if (outputLine.equals("Bye"))
break;
}
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
You can read more about sockets in Oracle tutorials
Related
I am currently working on a TCP Sockets program in Java in which two or more separate clients connect to a single server, and that server will send a message to both of these connected clients simultaneously.
I've tried to work through the code multiple times, but I can't quite seem to be able to have one message be sent to both clients.
Below is a reduced version of my entire code, condensed down to just the issue I'm having.
I've also included a video, just to save you the effort of having to copy and run my code!
[STREAMABLE LINK]
When one client is connected, I just have to write one message in the server, press send, and it shows up in the client.
When two clients are connected, I have to write two messages in the server and press send twice, and one message goes to one client and the other to the next client.
How can I make it so I only send one message from the server that goes to all clients?
I greatly appreciate any and all help.
SERVER CODE:
import java.io.*;
import java.net.*;
import java.util.*;
// Server class
class Server {
public class countLogic {
public static int client_count = 0;
}
public static void main(String[] args) {
System.out.println("[SERVER]");
ServerSocket server = null;
try {
server = new ServerSocket(1234);
server.setReuseAddress(true);
while (true) {
Socket client = server.accept();
countLogic.client_count++;
System.out.println("Client ("+countLogic.client_count+") connected: " + client.getInetAddress().getHostAddress());
ClientHandler clientSock = new ClientHandler(client);
new Thread(clientSock).start();
}
}
catch (IOException e) {
e.printStackTrace();
}
finally {
if (server != null) {
try {
server.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
}
}
// ClientHandler class
private static class ClientHandler implements Runnable {
private final Socket clientSocket;
public ClientHandler(Socket socket)
{
this.clientSocket = socket;
}
public void run()
{
PrintWriter out = null;
BufferedReader in = null;
try {
Scanner sc = new Scanner(System.in);
out = new PrintWriter(clientSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String line = null;
while (true) {
line = sc.nextLine();
out.println(line);
}
}
catch (IOException e) {
e.printStackTrace();
}
finally {
try {
if (out != null) {
out.close();
}
if (in != null) {
in.close();
clientSocket.close();
}
}
catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
CLIENT CODE:
import java.io.*;
import java.net.*;
import java.util.*;
// Client class
class Client {
// driver code
public static void main(String[] args)
{
System.out.println("[CLIENT 1]");
try (Socket socket = new Socket("localhost", 1234)) {
PrintWriter out = new PrintWriter(
socket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
Scanner sc = new Scanner(System.in);
String line = null;
while (!"exit".equalsIgnoreCase(line)) {
System.out.println("Server: "+ in.readLine());
}
// closing the scanner object
sc.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
}
Apologies as I asked something similar last night, but I have narrowed my problem down. I am wondering how to make my Java TCP Socket Server read in the data sent using the printWriter(out) in the Client code from a GUI as it does from the command line stdin.
I have the following classes as an example and everything works fine until the GUI comes into the equation. The data is being sent over to the Server from the GUI as I can echo it on the server side, but it is not being read and parsed properly as the stdin is. Nothing is being sent back to the client. I have tried flushing, using different streams and adding line separators all over the place to no avail. There is also a Protocol class that handles the data on the Server side.
public class KnockKnockServer {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(4444);
System.out.println("Waiting for client...");
} catch (IOException e) {
System.err.println("Could not listen on port: 4444.");
System.exit(1);
}
Socket clientSocket = null;
try {
clientSocket = serverSocket.accept();
} catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
}
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String inputLine, outputLine;
KnockKnockProtocol kkp = new KnockKnockProtocol();
outputLine = kkp.processInput(null);
out.println(outputLine);
while ((inputLine = in.readLine()) != null) {
System.out.println(inputLine);
outputLine = kkp.processInput(inputLine);
out.println(outputLine);
if (outputLine.equals("Bye.")) {
break;
}
}
out.close();
in.close();
clientSocket.close();
serverSocket.close();
}
}
.
public class KnockKnockClient {
public static PrintWriter out = null;
public static String sendAnswer;
public static void Client() {
//JButton Action Listener
saveAnswer.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
ButtonModel b = group.getSelection();
if (b.getActionCommand() == "A") { sendAnswer = radioA.getText(); }
String data = "รท" + sendAnswer;
out.println(data);
}
});
}
public static void main(String[] args) throws IOException {
KnockKnockClient.Client();
Socket kkSocket = null;
//PrintWriter out = null;
BufferedReader in = null;
try {
kkSocket = new Socket("localhost", 4444);
out = new PrintWriter(kkSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Don't know about host: localhost.");
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to: localhost.");
System.exit(1);
}
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
String fromServer, fromUser;
while ((fromServer = in.readLine()) != null) {
System.out.println("Server: " + fromServer);
if (fromServer.equals("Bye."))
break;
fromUser = stdIn.readLine();
if (fromUser != null) {
System.out.println("Client: " + fromUser);
out.println(fromUser);
}
}
out.close();
in.close();
stdIn.close();
kkSocket.close();
}
}
Hello I need some quick help with this Server/Client socket program I am writing in Java. Everything works as intended when entering standard input on the client side. The server responds with the correct data every time. But when I send data to the Server using the actionListener, nothing is returned. The data is being sent over and read by the Server and can be printed server-side, it just won't come back to the Client.
So this must be an issue with the formatting or type of data being sent from the actionListener (I don't know enough about streams unfortunately), or it is an issue with the stream on the server side?
Any help is most appreciated!
public class Serv {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(8889);
System.out.println("Waiting for client...");
} catch (IOException e) {
System.err.println("Could not listen on port: 8889.");
System.exit(1);
}
Socket clientSocket = serverSocket.accept();
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
String inputLine, outputLine;
Protocol p = new Protocol();
out.println("welcome");
while ((inputLine = in.readLine()) != null) {
outputLine = p.processInput(inputLine);
System.out.println("Input: "+inputLine + "\nOutput: "+outputLine);
out.println(outputLine);
if (outputLine.equals("Exit")) { break; }
}
out.close();
in.close();
clientSocket.close();
serverSocket.close();
}
}
public class Cl extends JFrame {
public static PrintWriter out = null;
public static String fromUser;
public static void Client() {
saveAnswer.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
ButtonModel b = group.getSelection();
if (b.getActionCommand() == "A") { sendAnswer = radioA.getText(); }
if (b.getActionCommand() == "B") { sendAnswer = radioB.getText(); }
if (b.getActionCommand() == "C") { sendAnswer = radioC.getText(); }
String data = "÷" + sendAnswer;
out.println(data);
}
});
}
public static void main(String[] args) throws IOException {
Socket Socket = null;
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
boolean checkOpen = false;
Socket clientS = new Socket("localhost", 8889);
out = new PrintWriter(clientS.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(clientS.getInputStream()));
String fromServer;
while ((fromServer = in.readLine()) != null) {
if (fromServer.startsWith("®")) {
if (checkOpen == false) { Cl.Client(); checkOpen = true; }
qA.splitter(fromServer);
}
if (fromServer.equals("Exit")) { break; }
fromUser = stdIn.readLine();
if (fromUser != null) {
System.out.println("Client: " + fromUser);
out.println(fromUser);
}
else { System.out.println("trouble"); }
}
out.close();
in.close();
stdIn.close();
Socket.close();
}
}
In the server, you're sending one line and then reading from the client until EOS.
In the client, you're reading from the server until EOS and then sending whatever the user types.
Your protocol doesn't make sense. All you have here is a deadlock.
You might need to do out.flush() after writing the response on the server side.
I'm trying to make a server/client to send text from client to server then sending back an ok message or something similar back to the client, but for some error that I can't see, either the server gets stuck right before sending the ok back to the client, or the client does not receive the message (I think it's the first one though).
Any help is appreciated.
This is the server code:
class ActiveServer extends Thread {
InputStream inStream;
OutputStream outStream;
public ActiveServer(InputStream inStream, OutputStream outStream) {
this.inStream = inStream;
this.outStream = outStream;
}
#Override
public void run() {
boolean ret = false;
try (BufferedReader reader = new BufferedReader(new InputStreamReader(inStream));
PrintWriter writer = new PrintWriter(outStream);) {
String line = null;
while((line = reader.readLine()) != null) {
String[] str = line.split(";");
line = null;
switch (str[0]) {
case "insert" : //ret = SQLOptions.insert(str[1], str[2]);
System.out.println(str[1]);
break;
}
writer.print(ret);
writer.flush();
// As far as i can see it gets stuck at the end of this while, but I don't know why.
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
public class Server {
private static final int PORT = 39165;
public static void main(String[] args) {
try (ServerSocket server = new ServerSocket(PORT);) {
System.out.println("Servidor online");
ExecutorService service = Executors.newFixedThreadPool(10);
while (true) {
Socket client = server.accept();
InetAddress ip = client.getInetAddress();
SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
Date time = new Date();
System.out.print(sdf.format(time));
System.out.println(" " + ip + " connected");
InputStream inStream = client.getInputStream();
OutputStream outStream = client.getOutputStream();
service.execute(new ActiveServer(inStream,outStream));
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
And here goes the client code:
public class Telnet {
static Console console = System.console();
public static void connect(String ip, String port) {
try(Socket socket = new Socket(ip, Integer.parseInt(port));
PrintWriter writer = new PrintWriter(socket.getOutputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));) {
String msg = null;
while(true) {
msg = console.readLine();
writer.println(msg);
writer.flush();
if (msg.equals(".quit")) {
System.out.println("Exiting...");
break;
}
String input = reader.readLine();
System.out.println(input);
}
} catch (NumberFormatException e) {
e.printStackTrace();
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
if(args.length < 2) {
err.println("Telnet <ip> <port>");
return;
}
if (console == null) {
err.println("A console is not available");
return;
}
connect(args[0], args[1]);
}
}
On the server side, you write the response without a terminating newline:
writer.print(ret);
But on the client side, you read until the end of line:
String input = reader.readLine();
The documentation for BufferedReader#readLine says:
Reads a line of text. A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed.
Thus, the client will wait forever for the newline sequence which the server will never send.
I am very new to sockets and was hoping someone could help me. I had something working but it was not sending information very quickly so i have refactored and now cannot get back to anything which works. The issue seems to be that only the first message that is published is read and then the receiver sits on client = listener.accept(); even though im pretty sure the sender is still sending messages
Can anyone see what i might be doing wrong here please?
Thanks
public class Sender {
Socket server = null;
DataInputStream inp = null;
PrintStream outp = null;
public Sender(){
server = new Socket("127.0.0.1" , 3456);
outp = new PrintStream(server.getOutputStream());
}
private void connectAndSendToServer(String message) {
outp = new PrintStream(server.getOutputStream());
outp.print(message + "\n");
outp.flush();
}
}
Receiver class
public class Receive{
public String receiveMessage(int port) {
String message= null;
ServerSocket listener = null;
Socket client = null;
try{
listener = new ServerSocket(port);
client = listener.accept();
BufferedReader br = new BufferedReader(new InputStreamReader(client.getInputStream()));
return br.readLine();
}
...
finally{
try {
if(client!=null && listener!=null){
client.close();
listener.close();
}
}
catch (IOException e) {
}
}
return message;
}
}
This because a ServerSocket is used as an entry point for a normal Socket. accept() is a blocking operation that is usually done on a different thread compared to the one that receives/sends data to normal Socket. It sits there and waits for a new connection to spawn a new Socket which is then used for data.
This means that while receiving messages you should call just readLine() to read from the specific Socket. Having an accept inside the receiveMessage is wrong just because it's a different operation and it's even blocking.
Socket socket = serverSocket.accept();
ClientThread thread = new ClientThread(socket);
class ClientThread extends Thread {
Socket socket;
public void run() {
while (!closed) {
String line = reader.readLine();
...
}
}
You don't need to have a thread for every client though, but you need at least two for sure if you want to make your server accept a number of connections greater than 1.
You are not using ServerSocket correctly. You shouldn't create a new instance for every message but use it as a data member maybe and run an infinite loop to get a new client socket connection. Because you create it locally, the socket is closed since the object is no longer used and referenced (and so GC'ed), when you return from the method.
Something like (< condition met > is pseudo-code defines your condition to accept new connections):
while(< condition met >) {
try {
client = listener.accept();
BufferedReader br = new BufferedReader(new InputStreamReader(client.getInputStream()));
String str = br.readLine();
//do something with str
} finally {
//close client socket
}
}
Better approach will be to handle client socket in a different thread so the main thread is back to accept while you can do anything with the client socket in parallel.
Try this basic Chatting Server written by me. This server simply keeps running in loop and broadcast the message send by the clients to all the other clients associated with this server.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
public class Server {
// ///----------------------------------------Instance Variable Fields
ServerSocket ss = null;
Socket incoming = null;
// ///----------------------------------------Instance Variable Fields
// ///---------------------------------------- static Variable Fields
public static ArrayList<Socket> socList = new ArrayList<Socket>();
// ///---------------------------------------- static Variable Fields
public void go() {
try {
ss = new ServerSocket(25005);
while (true) {
incoming = ss.accept();
socList.add(incoming);
System.out.println("Incoming: " + incoming);
new Thread(new ClientHandleKaro(incoming)).start();
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
ss.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
class ClientHandleKaro implements Runnable {
InputStream is = null;
OutputStream os = null;
InputStreamReader isr = null;
BufferedReader br = null;
PrintWriter pw = null;
boolean isDone = false;
Socket sInThread = null;
public ClientHandleKaro(Socket sxxx) {
this.sInThread = sxxx;
}
#Override
public void run() {
if (sInThread.isConnected()) {
System.out.println("Welcamu Clienta");
System.out.println(socList);
}
try {
is = sInThread.getInputStream();
System.out.println("IS: " + is);
isr = new InputStreamReader(is);
br = new BufferedReader(isr);
os = sInThread.getOutputStream();
pw = new PrintWriter(os, true);
String s = new String();
while ((!isDone) && (s = br.readLine()) != null) {
String[] asx = s.split("-");
System.out.println("On Console: " + s);
// pw.println(s);
Thread tx = new Thread(new ReplyKaroToClient(s,
this.sInThread));
tx.start();
if (asx[1].trim().equalsIgnoreCase("BYE")) {
System.out.println("I am inside Bye");
isDone = true;
}
}
} catch (IOException e) {
System.out.println("Thanks for Chatting.....");
} finally {
try {
Thread tiku = new Thread(new ByeByeKarDo(sInThread));
tiku.start();
try {
tiku.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Accha to hum Chalte hain !!!");
System.out.println(socList);
br.close();
pw.close();
sInThread.close();
} catch (IOException e) {
}
}
}
}
class ReplyKaroToClient implements Runnable {
public String mString;
public Socket mSocket;
public ReplyKaroToClient(String s, Socket sIn) {
this.mString = s;
this.mSocket = sIn;
}
#Override
public void run() {
for (Socket sRaW : socList) {
if (mSocket.equals(sRaW)) {
System.out.println("Mai same hun");
continue;
} else {
try {
new PrintWriter(sRaW.getOutputStream(), true)
.println(mString);
} catch (IOException e) {
System.out.println("Its in Catch");
}
}
}
}
}
class ByeByeKarDo implements Runnable {
Socket inCom;
public ByeByeKarDo(Socket si) {
this.inCom = si;
}
#Override
public void run() {
try {
new PrintWriter(inCom.getOutputStream(), true)
.println("You have Logged Out of Server... Thanks for your Visit");
} catch (IOException e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) {
new Server().go();
}
}