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Socket Crashes Thread

Problem:
My #Override run() method which is part of the class that implements Runnable, is called constantly like normal. However, the moment I open up a socket connection, that thread seems to stop, without throwing any errors. If I connect the client to a server socket, it works just fine, however the GUI which is being ticked by the #Override run() method just stops working
Run Method:
#Override
public void run()
{
}
Server Socket (which stops the run() method from being invoked):
public class CommonProxy
{
public static boolean isActive = false;
public static void startServer() throws IOException
{
isActive = true;
Socket socket;
OutputStreamWriter outputStreamWriter;
InputStreamReader inputStreamReader;
BufferedWriter bufferedWriter;
BufferedReader bufferedReader;
ServerSocket serverSocket;
serverSocket = new ServerSocket(1234);
while (isActive)
{
try
{
socket = serverSocket.accept();
System.out.println("hi");
outputStreamWriter = new OutputStreamWriter(socket.getOutputStream());
inputStreamReader = new InputStreamReader(socket.getInputStream());
bufferedWriter = new BufferedWriter(outputStreamWriter);
bufferedReader = new BufferedReader(inputStreamReader);
while (isActive)
{
String clientMessage = bufferedReader.readLine();
System.out.println("[Client]: " + clientMessage);
bufferedWriter.write("Message Recieved");
bufferedWriter.newLine();
bufferedWriter.flush();
if (clientMessage.equalsIgnoreCase("exit"))
{
System.out.println("Client Disconnected");
break;
}
}
socket.close();
inputStreamReader.close();
outputStreamWriter.close();
bufferedReader.close();
bufferedWriter.close();
} catch (IOException e)
{
e.printStackTrace();
}
}
}
}
Client socket (which also stops the method from being invokes) if needed:
public static void startClient(String address, int port)
{
isActive = true;
Socket socket = null;
OutputStreamWriter outputStreamWriter = null;
InputStreamReader inputStreamReader = null;
BufferedWriter bufferedWriter = null;
BufferedReader bufferedReader = null;
try
{
socket = new Socket("192.168.0.100", 1234);
System.out.println(socket.getLocalAddress().getHostAddress());
outputStreamWriter = new OutputStreamWriter(socket.getOutputStream());
inputStreamReader = new InputStreamReader(socket.getInputStream());
bufferedWriter = new BufferedWriter(outputStreamWriter);
bufferedReader = new BufferedReader(inputStreamReader);
Scanner scanner = new Scanner(System.in);
while (isActive)
{
String queuedMessage = scanner.nextLine();
bufferedWriter.write(queuedMessage);
bufferedWriter.newLine();
bufferedWriter.flush();
System.out.println(bufferedReader.readLine());
if (queuedMessage.equalsIgnoreCase("exit"))
break;
}
}
catch(IOException e)
{
e.printStackTrace();
}
finally
{
try
{
if (socket != null) socket.close();
if (inputStreamReader != null) inputStreamReader.close();
if (outputStreamWriter != null) outputStreamWriter.close();
if (bufferedReader != null) bufferedReader.close();
if (bufferedWriter != null) bufferedWriter.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
public static void queueMessage(String message)
{
queuedMessage = message;
}
public static String getMessage()
{
return lastServerMessage;
}

Handle more clients

Right now my server only can handle one client at a time. I am trying to use a Thread so that the server can handle several clients, but I am doing it wrong. I have added the thread in the try/catch clause where the serverSocket accepts the client, but this makes no difference. I don't get an error or anything, but it just doesn't work.
So what I want to do, is make the server not freeze at one client, but still accept several clients.
Here is the server code:
import java.io.*;
import java.net.*;
public class Server {
private BufferedReader reader;
private PrintWriter writer;
private int port;
public Server(int port)
{
this.port = port;
}
private String getSeverAddress() {
String host = null;
try {
InetAddress adr = InetAddress.getLocalHost();
host = adr.getHostAddress();
} catch (UnknownHostException e) {
e.printStackTrace();
}
return host;
}
public void startServer() {
print("Contact this sever on address: " + getSeverAddress() + " port: " + port);
ServerSocket ss = null;
Socket socket = null;
Thread clientThread = null;
try {
ss = new ServerSocket(port);
socket = ss.accept();
clientThread = new Thread(new Client(socket));
clientThread.start();
reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
writer = new PrintWriter(socket.getOutputStream(), true);
String msg = null;
while (( msg = reader.readLine()) != null) {
print("System out: " + msg);
if(msg.equals("Bye")) {
print("Client left");
break;
}
}
ss.close();
socket.close();
reader.close();
writer.close();
} catch(SocketException e) {
e.printStackTrace();
} catch (IOException i ) {
i.printStackTrace();
return;
}
}
private void print(String msg) {
System.out.println(msg);
}
public static void main(String[] args) {
Server server = new Server(1111);
server.startServer();
}
}
Here is the client code:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
public class Client implements Runnable{
private Socket client;
private BufferedReader reader;
private PrintWriter writer;
public Client(Socket socket)
{
client = socket;
try{
reader = new BufferedReader(new InputStreamReader(client.getInputStream()));
writer = new PrintWriter(client.getOutputStream(), true);
} catch (Exception e) {
e.printStackTrace();
return;
}
}
#Override
public void run() {
String msg = null;
BufferedReader r = null;
try {
r = new BufferedReader(new InputStreamReader(System.in));
} catch (Exception e1) {
e1.printStackTrace();
}
System.out.println("Write message to server");
while(true) {
try {
msg = r.readLine();
if(msg.equals("Quit") || msg == null) {
print("Disconnect");
break;
}
} catch (IOException e) {
e.printStackTrace();
}
writeToServer(msg);
}
try {
r.close();
} catch (IOException e) {
e.printStackTrace();
}
}
public void writeToServer(String msg) {
writer.println(msg);
}
private void print(String msg) {
System.out.println(msg);
}
public static void main(String[] args) {
Socket socket = null;
try {
socket = new Socket("localhost", 1111);
} catch (Exception e) {
e.printStackTrace();
}
Client client = new Client(socket);
client.run();
}
}

You are still trying to handle clients in your main thread. Main thread should just accept new connections and start new threads. You also have to do accept in a loop so multiple connections can be accepted:
ss = new ServerSocket(port);
while(true) {
Socket socket = ss.accept();
Thread clientThread = new Thread(new Runnable() {
public void run() {
BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
String msg = null;
while (( msg = reader.readLine()) != null) {
print("System out: " + msg);
if(msg.equals("Bye")) {
print("Client left");
break;
}
}
socket.close();
reader.close();
writer.close();
}});
clientThread.start();
}

You need to put your ss.accept() into a while loop and create a new Thread for every client accepted, which handles the connection.

BufferedReader from server does not work

In this code I can correctly receive a request using BufferedReader inClient, created on the client socket.
Then I send the request to the server and I see the server gets it.
But then, when I try to read the reply from the server (using BufferedReader inServer on the socket of the server), it always ends in IOException: Impossible read from server.
I am referring to the block ################
Do you know any possible reasons?
import java.io.*;
import java.net.Socket;
import java.net.ServerSocket;
import java.net.InetAddress;
import java.net.UnknownHostException;
public class ProxyMain {
public static void main(String argv[]) {
int proxyPort = 55554;
String proxyAddr = "127.0.0.1";
ServerSocket proxySocket = null;
try {
proxySocket = new ServerSocket(proxyPort, 50, InetAddress.getByName("127.0.0.1"));
}
catch (Exception e) {
System.err.println("Impossible to create socket server!");
System.out.flush();
System.exit(1);
}
System.out.printf("Proxy active on port: %d and on address %s\n", proxyPort, proxySocket.getInetAddress());
System.out.println();
while (true) {
Socket client = null;
Socket sockServ = null;
BufferedReader inClient = null;
PrintWriter outClient = null;
BufferedReader inServer = null;
PrintWriter outServer = null;
String request = new String();
String tmp = new String();
String reply = new String();
String tmpReply = new String();
try {
client = proxySocket.accept();
System.out.println("Connected to: ");
System.out.println(client.getInetAddress().toString());
System.out.printf("On port %d\n", client.getPort());
System.out.println();
inClient = new BufferedReader(new InputStreamReader(client.getInputStream()));
outClient = new PrintWriter(client.getOutputStream(), true);
}
/*catch (IOException e) {
System.err.println("Couldn't get I/O for connection accepted");
System.exit(1);
}*/
catch (Exception e) {
System.out.println("Error occurred!");
System.exit(1);
}
System.out.println("Received request:");
try{
for (int i = 0; i<2; i++) {
tmp = inClient.readLine();
request = request + tmp;
}
inClient.close();
}
catch (IOException ioe) {
System.err.println("Impossible to read mhttp request!");
System.exit(1);
}
System.out.println(request);
System.out.println();
try {
sockServ = new Socket("127.0.0.1", 55555);
outServer = new PrintWriter(sockServ.getOutputStream(), true);
inServer = new BufferedReader(new InputStreamReader(sockServ.getInputStream()));
}
catch (UnknownHostException e) {
System.err.println("Don't know about host: 127.0.0.1:55555");
System.exit(1);
}
catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to: 127.0.0.1:55555");
System.exit(1);
}
outServer.println(request);
outServer.close();
try {
#################################################
while ((tmpReply = inServer.readLine()) != null) {
System.out.println(tmpReply);
reply = reply + tmpReply;
}
inServer.close();
sockServ.close();
}
catch (IOException ioe) {
System.err.println("Impossible to read from server!");
System.exit(1);
}
outClient.println(reply);
outClient.close();
try {
client.close();
}
catch (IOException ioe) {
System.err.printf("Impossible to close connection with %s:%d\n", client.getInetAddress().toString(), client.getPort());
}
}
}
}
UPDATE:
It seems that if I do:
boolean res = inServer.ready();
it always return false.
So Server is not ready to send the reply but this is strange...with my Project in C e Python it worked immediately. Why should java be different?

When you close outServer, you close the underlying socket. if you just want to close the output and keep the input open, you need to use Socket.shutdownOutput(). note, you have the same problem when you close inClient.

This works, maybe you can get some ideas from it...
ChatServer - broadcasts to all connected clients
In one command prompt: java ChartServer
In another: java ChatClient localhost (or the ip address of where the server is running)
And another: java ChatClient localhost (or the ip address of where the server is running)
Start chatting in the client windows.
Server like this...
// xagyg wrote this, but you can copy it
import java.io.*;
import java.net.*;
import java.util.*;
public class ChatServer {
public static List list = new ArrayList();
public static void main(String[] args) throws Exception {
ServerSocket svr = new ServerSocket(4444);
System.out.println("Chat Server started!");
while (true) {
try {
Socket s = svr.accept();
synchronized(list) {
list.add(s);
}
new Handler(s, list).start();
}
catch (IOException e) {
// print out the error, but continue!
System.err.println(e);
}
}
}
}
class Handler extends Thread {
private Socket s;
private String ipaddress;
private List list;
Handler (Socket s, List list) throws Exception {
this.s = s;
ipaddress = s.getInetAddress().toString();
this.list = list;
}
public void run () {
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(s.getInputStream()));
String message;
//MyDialog x = (MyDialog)map.get(ipaddress.substring(1));
while ((message = reader.readLine()) != null) {
if (message.equals("quit")) {
synchronized(list) {
list.remove(s);
}
break;
}
synchronized(list) {
for (Object object: list) {
Socket socket = (Socket)object;
if (socket==s) continue;
PrintWriter writer = new PrintWriter(socket.getOutputStream());
writer.println(ipaddress + ": " + message);
writer.flush();
}
}
}
try { reader.close(); } catch (Exception e) {}
}
catch (Exception e) {
System.err.println(e);
}
}
}
Client like this ...
// xagyg wrote this, but you can copy it
import java.util.*;
import java.io.*;
import java.net.*;
public class ChatClient {
public static void main(String[] args) throws Exception {
Socket s = new Socket(args[0], 4444);
BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));
PrintWriter out = new PrintWriter(s.getOutputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String message;
new SocketReader(in).start();
while ((message = reader.readLine())!=null) {
out.println(message);
out.flush();
if (message.equals("quit")) break;
}
in.close();
out.close();
}
}
class SocketReader extends Thread {
BufferedReader in;
public SocketReader(BufferedReader in) {
this.in = in;
}
public void run() {
String message;
try {
while ((message = in.readLine())!=null) {
System.out.println(message);
}
}
catch (Exception e) {
throw new RuntimeException(e);
}
}
}

BufferedWriter.write() does not seem to work

I have two Java applications, where an Android client connects to a server on a computer and sends a message using BufferedWriter over websockets.
The client:
try {
toast("Sending...");
Socket sock = new Socket(ip, PORT);
OutputStream os = sock.getOutputStream();
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(os));
bw.flush();
bw.write("Hello Server!");
toast("Connected!");
} catch (UnknownHostException e) {
toast(e.getMessage());
} catch (IOException e) {
toast(e.getMessage());
}
The server:
public static void main(String[] args) {
ServerSocket server;
ConnectionThread ct;
Socket s;
ExecutorService es = Executors.newSingleThreadExecutor();
try {
System.out.println("Starting server...");
server = new ServerSocket(1337);
s = server.accept();
ct = new ConnectionThread(s);
es.execute(ct);
} catch (IOException ex) {
ex.printStackTrace();
}
}
The ConnectionThread class:
public class ConnectionThread implements Runnable {
private Socket sock;
private InputStream is;
private BufferedReader br;
private boolean online;
public ConnectionThread(Socket s) {
System.out.println("Creating connection thread.");
this.sock = s;
online = true;
}
#Override
public void run() {
String input = "";
try {
System.out.println("Starting to read...");
is = sock.getInputStream();
br = new BufferedReader(new InputStreamReader(is));
while (online) {
input = br.readLine();
if(input != null){
System.out.print("Received message: ");
System.out.println(input);
}
}
br.close();
is.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
When I run the server, and then the client, the client will show the "Connected!" toast, and the server's output will be:
Starting server...
Creating connection thread.
Starting to read...
So, it seems like the connection is actually being made, but the message does not arrive. Does anybody know why this could be happening?

Your server is expecting a complete line terminated by a newline. Try:
bw.write("Hello Server!");
bw.newLine();

Do it like this...
String s = new String();
while ((br.readLine())!=null) {
s = s+br.readLine();
System.out.print("Received message: ");
System.out.println(input);
}
}
And
bw.println("Hello Server");

I notice that you don't send an endline on your client, so the BufferedReader.readline() will never return, because it cannot match the \n-character. Try it again with
bw.write("Hello Server!\n");
on the client side.

How can I transfer files from Server-Side to Client using Sockets?

I'm having trouble on where to begin performing this task, I'd like some examples or input on how I should set up my server/client components to receive and send data including letting the client download images.
Here's my client-side code:
package V3;
import java.io.*;
import java.net.*;
public class Version3Client {
public static void main(String[] args) throws IOException {
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: taranis.");
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to: taranis.");
System.exit(1);
}
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
String fromServer;
String 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();
}
}
And here's my server-side code:
package V3;
import java.net.*;
import java.io.*;
public class Version3Server {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
boolean listening = true;
try {
serverSocket = new ServerSocket(4444);
} catch (IOException e) {
System.err.println("Could not listen on port: 4444.");
System.exit(-1);
}
while (listening)
new Version3ServerThread(serverSocket.accept()).start();
serverSocket.close();
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;
Version3Protocol kkp = new Version3Protocol();
outputLine = kkp.processInput(null);
out.println(outputLine);
while ((inputLine = in.readLine()) != null) {
outputLine = kkp.processInput(inputLine);
out.println(outputLine);
if (outputLine.equals("Bye."))
break;
}
out.close();
in.close();
clientSocket.close();
serverSocket.close();
}
}
Thread class added for further specification:
package V3;
import java.net.*;
import java.io.*;
import java.io.FileWriter;
public class Version3ServerThread extends Thread {
private Socket socket = null;
public Version3ServerThread(Socket socket) {
super("Version3ServerThread");
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;
Version3Protocol kkp = new Version3Protocol();
outputLine = kkp.processInput(null);
out.println(outputLine);
while ((inputLine = in.readLine()) != null) {
outputLine = kkp.processInput(inputLine);
out.println(outputLine);
if (outputLine.equals("Bye"))
break;
if(kkp.getInteraction()){
Logging.writeToFile(socket.getInetAddress());
}
}
out.close();
in.close();
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

The code so far, the client-server-communication without the file-transfer ability, looks fine to me. I wanted to compile to find any errors but you didnt include Version3Protocol and Logging. If it does compile then your next step would be to open the file you want to transfer on the server with a FileInputStream and a new file for writing on the client with FileOutputStream:
http://download.oracle.com/javase/1.4.2/docs/api/java/io/FileInputStream.html
http://download.oracle.com/javase/1.4.2/docs/api/java/io/FileOutputStream.html
You can then read the file into buffer, transfer it using the socket, receive it on the client-side, and copy the buffer-contents into the FileOutputStream there.