Hi I am trying to set up a ServerSocket in java and I have kept the backlog level to default 50. I have 5 clients trying to connect to the server at almost the same time. Sometimes everything goes smoothly while sometimes some of the client's connections are refused by the server. I have tried increasing backlog value to 100 but no luck. I am using Ubuntu 13.10. Any ideas?
package networkmodule;
import iomodule.FileHandler;
import java.io.*;
import java.net.*;
import java.util.*;
public class FileReceiveServer implements Runnable {
private ServerSocket server;
private int receiveport;
private boolean isMaster;
private boolean isStats;
private ArrayList<Thread> clientThreads;
private int totalClients;
private int clientsReceived;
public FileReceiveServer(int receiveport, boolean isMaster, boolean isStats) {
this.receiveport = receiveport;
this.isMaster = isMaster;
this.isStats = isStats;
clientThreads = new ArrayList<Thread>();
if (isMaster && !isStats) {
totalClients = ((Hashtable<String, String>) FileHandler.loadObject("clientstats")).size();
clientsReceived = 0;
}
try {
server = new ServerSocket(receiveport);
} catch (IOException e) {
e.printStackTrace();
}
}
public void run() {
try {
while (true) {
Socket clientSocket = server.accept();
Thread newClientThread = new Thread(new FileReceiverThread(clientSocket, isMaster, isStats));
clientThreads.add(newClientThread);
newClientThread.start();
if (isMaster && !isStats) {
clientsReceived++;
}
}
} catch (IOException e) {
}
}
public boolean checkThreadCompletion() {
if (isMaster) {
if (clientsReceived < totalClients) {
return false;
}
if (clientThreads.size() > 0) {
for (Thread t : clientThreads) {
if (t != null) {
if (t.isAlive()) {
return false;
}
}
}
return true;
}
return false;
} else {
if (clientThreads.size() > 0) {
for (Thread t : clientThreads) {
if (t != null) {
if (t.isAlive()) {
return false;
}
}
}
return true;
}
return false;
}
}
public void stopServer() {
try {
server.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
This is quite a simple code and I have no idea why it fails sometimes. Here the important thing is that it fails only sometimes not always, and when it fails, it always fails on client side when I try to make a socket to connect to the server with:
java.net.ConnectException: Socket Connection Refused
Any ideas?
Thanks
Related
I have to create a simple rotating proxy application where 100 requests get evenly distributed to 10 devices. I've got the following structure:
WebServer with a Java-SocketServer running. All Android devices are connected to this Socket-Server to be able to know which devices are currently online and for determining which device should be used for the next request.
10 Android devices in different networks. They are connected to the Socket Server and are waiting for requests that should be forwarded to the remote address and then sent back to the SocketServer.
In easy words: I basically have to create an application similar like Honeygain, Peer2Profit or IPRoyal Pawns so that I can later do requests like this:
//Use "-x" to set Proxy-IP and Proxy-Port
curl -x ANDROID_DEVICE_IP:PORT -L https://www.google.com
I managed to have an always running proxy service in an Android application. It basically looks like this and just forwards HTTP-Requests from Port 1440 to the desired remote address and then sends the response back to the original client. The Proxy basically works fine.
public class ProxyServerThread extends Thread {
public static void main(String[] args) {
(new ProxyServerThread()).run();
}
public ProxyServerThread() {
super("Server Thread");
}
#Override
public void run() {
try (ServerSocket serverSocket = new ServerSocket(1440)) {
Socket socket;
try {
while ((socket = serverSocket.accept()) != null) {
(new Handler(socket)).start();
}
} catch (IOException e) {
e.printStackTrace(); // TODO: implement catch
}
} catch (IOException e) {
e.printStackTrace(); // TODO: implement catch
return;
}
}
public static class Handler extends Thread {
public static final Pattern CONNECT_PATTERN = Pattern.compile("CONNECT (.+):(.+) HTTP/(1\\.[01])", Pattern.CASE_INSENSITIVE);
private final Socket clientSocket;
private boolean previousWasR = false;
public Handler(Socket clientSocket) {
this.clientSocket = clientSocket;
}
#Override
public void run() {
try {
String request = readLine(clientSocket);
System.out.println(request);
Matcher matcher = CONNECT_PATTERN.matcher(request);
if (matcher.matches()) {
String header;
do {
header = readLine(clientSocket);
} while (!"".equals(header));
OutputStreamWriter outputStreamWriter = new OutputStreamWriter(clientSocket.getOutputStream(), "ISO-8859-1");
final Socket forwardSocket;
try {
forwardSocket = new Socket(matcher.group(1), Integer.parseInt(matcher.group(2)));
System.out.println(forwardSocket);
} catch (IOException | NumberFormatException e) {
e.printStackTrace(); // TODO: implement catch
outputStreamWriter.write("HTTP/" + matcher.group(3) + " 502 Bad Gateway\r\n");
outputStreamWriter.write("Proxy-agent: Simple/0.1\r\n");
outputStreamWriter.write("\r\n");
outputStreamWriter.flush();
return;
}
try {
outputStreamWriter.write("HTTP/" + matcher.group(3) + " 200 Connection established\r\n");
outputStreamWriter.write("Proxy-agent: Simple/0.1\r\n");
outputStreamWriter.write("\r\n");
outputStreamWriter.flush();
Thread remoteToClient = new Thread() {
#Override
public void run() {
forwardData(forwardSocket, clientSocket);
}
};
remoteToClient.start();
try {
if (previousWasR) {
int read = clientSocket.getInputStream().read();
if (read != -1) {
if (read != '\n') {
forwardSocket.getOutputStream().write(read);
}
forwardData(clientSocket, forwardSocket);
} else {
if (!forwardSocket.isOutputShutdown()) {
forwardSocket.shutdownOutput();
}
if (!clientSocket.isInputShutdown()) {
clientSocket.shutdownInput();
}
}
} else {
forwardData(clientSocket, forwardSocket);
}
} finally {
try {
remoteToClient.join();
} catch (InterruptedException e) {
e.printStackTrace(); // TODO: implement catch
}
}
} finally {
forwardSocket.close();
}
}
} catch (IOException e) {
e.printStackTrace(); // TODO: implement catch
} finally {
try {
clientSocket.close();
} catch (IOException e) {
e.printStackTrace(); // TODO: implement catch
}
}
}
private static void forwardData(Socket inputSocket, Socket outputSocket) {
try {
InputStream inputStream = inputSocket.getInputStream();
try {
OutputStream outputStream = outputSocket.getOutputStream();
try {
byte[] buffer = new byte[4096];
int read;
do {
read = inputStream.read(buffer);
if (read > 0) {
outputStream.write(buffer, 0, read);
if (inputStream.available() < 1) {
outputStream.flush();
}
}
} while (read >= 0);
} finally {
if (!outputSocket.isOutputShutdown()) {
outputSocket.shutdownOutput();
}
}
} finally {
if (!inputSocket.isInputShutdown()) {
inputSocket.shutdownInput();
}
}
} catch (IOException e) {
e.printStackTrace(); // TODO: implement catch
}
}
private String readLine(Socket socket) throws IOException {
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
int next;
readerLoop:
while ((next = socket.getInputStream().read()) != -1) {
if (previousWasR && next == '\n') {
previousWasR = false;
continue;
}
previousWasR = false;
switch (next) {
case '\r':
previousWasR = true;
break readerLoop;
case '\n':
break readerLoop;
default:
byteArrayOutputStream.write(next);
break;
}
}
return byteArrayOutputStream.toString("ISO-8859-1");
}
}
}
Here comes the Problem:
Everything works fine but only on the local network. I cannot manage to get this to work without port forwarding. Since all devices are on their mobile cellular data I need a way to be able to connect to the device anyway.
How do the mentioned apps manage to connect to the devices?
So, I'm fairly new to sockets and data streams... And I am absolutely baffled by this issue I'm having. I've searched for hours trying to find a solution, assuming that other people might have had the same issue I'm having, but I've found absolutely nothing helpful so far.
I'm writing a very simple multithreaded server/client program that is supposed to open a serverSocket, and accept connections from clients, storing them in a simple arraylist (I'll change the storage process once I actually get messages to send), and then a message handler thread parses the list, and checks if a user has written to the server. If the user has written something, the program then displays the resulting message to the console. My program successfully writes to the server socket through the DataOutputStream, but when I attempt to read from the corresponding DataInputStream on the server side, it says the stream is empty, and my program will continue to loop. I've checked that the DataOutputStream receives the data through DataOutputStream.size(), and that the DataInputStream I am attempting to read data from corresponds to the correct DataOutputStream I mentioned before.
User Code:
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.SocketException;
public class User {
private String hashID;
private Socket connection;
private static int hashVal = 0;
DataInputStream consoleInputStream;
String consoleInput = "";
public User(Socket conn) throws SocketException {
hashID = hashUserKey();
connection = conn;
connection.setSoTimeout(1500);
consoleInputStream = new DataInputStream(System.in);
}
private static String hashUserKey() { //placeholder for now
hashVal++;
return("Guest" + hashVal);
}
public Socket getSocket() {
return this.connection;
}
public String getID() {
return this.hashID;
}
public boolean disconnect() {
try {
consoleInputStream.close();
connection.close();
return true;
} catch (IOException e) {
System.err.println(hashID + " was unable to successfully disconnect");
return false;
}
}
public void startConnection() {
new Thread() {
#Override
public void run() {
while(!connection.isClosed()) {
try {
consoleInput = consoleInputStream.readLine();
if(consoleInput != null || consoleInput != "") {
writeToServer(consoleInput);
}
} catch (IOException e) {
System.err.println("Was not able to read console input");
}
}
System.out.println("You were disconnected, have a nice day!");
return;
}
}.start();
}
private boolean writeToServer(String toWrite) {
try {
String msg = hashID + ">>>: " + toWrite;
DataOutputStream outStream = new DataOutputStream(connection.getOutputStream());
outStream.writeUTF(toWrite + "\r\n");
outStream.flush();
consoleInput = "";
System.out.println(msg + "\t was written to " + connection.getInetAddress() + ":" + connection.getPort());
return true;
} catch (IOException e) {
System.err.println(hashID + " was unable to write to server");
return false;
}
}
#Override
public boolean equals(Object o) {
User t = (User) o;
if(t.hashID == this.hashID) {
return true;
}
return false;
}
}
Server Code:
import java.net.*;
import java.io.*;
import java.util.*;
public class TestServer {
private static ServerSocket server;
private static TestLogger logger;
private static Thread serverHandlerThread;
private static Thread messageHandlerThread;
private static ArrayList<User> users;
private static volatile boolean hasBeenStopped = false;
public static boolean startServer(int port) {
logger = new TestLogger();
logger.log("Attempting to create default shutdown behavior for server");
Runtime.getRuntime().addShutdownHook(new Thread() {
#Override
public void run() {
if(!hasBeenStopped) {
logger.warn("Server was shut down without running stopServer(), running by default");
stopServer();
}
}
}
);
logger.log("Shutdown behaivor created. Now attempting to set up user database"/*TODO create a real database*/);
users = new ArrayList<User>();
logger.log("Attempting to start server");
try {
server = new ServerSocket(port);
logger.log("Server successfully started at " + server.getInetAddress() + ":" + server.getLocalPort() +", now attempting to start user connection handler");
serverHandlerThread = new Thread() {
#Override
public void run() {
this.setName("serverHandlerThread");
while(!server.isClosed()) {
try {
Socket temp = server.accept();
logger.log("Connection accepted from " + temp.getInetAddress());
System.out.println("Connection accepted from " + temp.getInetAddress());
startUserConnection(new User(temp));
} catch (SocketException e) {
logger.warn("Server was closed while in accept phase");
} catch (IOException e) {
e.printStackTrace();
}
}
logger.log(this.getName() + " was stopped, server socket was closed successfully");
return;
}
};
serverHandlerThread.start();
logger.log("Server thread successfully started, listening for connections on: " + server.getInetAddress().toString() + ":" + port);
logger.log("Attempting to start message handler thread to read user inputs");
messageHandlerThread = new Thread() {
#Override
public void run() {
this.setName("messageHandlerThread");
while(!server.isClosed()) {
if(users.isEmpty()) {
continue;
}
for(int i = 0; i < users.size(); i++) {
User temp = users.get(i);
try {
System.out.println(new DataInputStream(temp.getSocket().getInputStream()).readUTF());
} catch (IOException e) {
System.err.println("Nothing to read from client: " + temp.getID());
}
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
};
messageHandlerThread.start();
return true;
} catch (IOException e) {
logger.error("Could not bind server socket to port.");
return false;
}
}
public static boolean stopServer() {
logger.log("Started shut down process");
if(serverHandlerThread == null || !serverHandlerThread.isAlive()) {
logger.warn("Thread has not been started yet or has already been killed");
return false;
}
else {
stopAllUserConnections();
try {
server.close();
hasBeenStopped = true;
while(serverHandlerThread.isAlive()) {
}
logger.log("Server was successfully shut down");
return true;
} catch (IOException e) {
logger.error("Could not close server socket");
return false;
}
}
}
private static void startUserConnection(User user) {
logger.log("Connected new user from " + user.getSocket().getInetAddress());
users.add(user);
System.out.println(user.getID() + " was added to list");
user.startConnection();
}
private static boolean stopUserConnection(User user) {
logger.log("Attempting to disconnect user, address: " + user.getSocket().getInetAddress());
for(User u : users) {
if(u.equals(user)) {
u.disconnect();
return true;
}
}
logger.warn("Could not find user with address: " + user.getSocket().getInetAddress());
return false;
}
private static boolean stopAllUserConnections() {
logger.log("Attempting to disconnect all users from the server");
if(users.isEmpty()) {
logger.warn("No users available to disconnect");
return false;
}
for(User u : users) {
u.disconnect();
}
users.clear();
return true;
}
public static void main(String args[]) {
startServer(*the_port*);
Client c = new Client();
c.connect("0.0.0.0", *the_port*);
}
}
Client Code:
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;
public class Client {
public boolean connect(String serverName, int port) {
try {
System.out.println("Attempting to connect");
Socket sock = new Socket(serverName, port);
System.out.println("Connected");
return true;
} catch (UnknownHostException e) {
System.err.println("Could not resolve " + serverName + ":" + port);
}
catch (IOException e) {
e.printStackTrace();
}
return false;
}
}
So as I said above, this works fine up until I attempt to read the data written to the server. No matter what I do, the server's call to readUTF() on the socket always throws an IOException and checking the bytes ready to read by using DataInputStream.available() returns 0 as well. My sample output from my most recent run is as follows:
Attempting to connect
Connected
Connection accepted from *the_address*
Guest1 was added to list
Nothing to read from client: Guest1
Nothing to read from client: Guest1
Nothing to read from client: Guest1
test
Guest1>>>: test was written to *the_address:another_port*
Nothing to read from client: Guest1
Nothing to read from client: Guest1
Nothing to read from client: Guest1
I know my code may be terribly optimized, and I'll work on fixing that later, but right now, all I want to know is why my DataInputStream is empty after flushing the corresponding DataOutputStream, and how I can successfully send UTF data between them.
This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 6 years ago.
I'm pretty new to this whole "Sockets" and networking world.
First, I wanted to make a random chat program like "omegle" and it worked perfectly fine. I think I had some serious issues in the code, but it worked - so why bother? (I wish I did).
Now I am adding a "Multiplayer" option in my "Tic Tac Toe" game in android, it went wrong and I spent many hours figuring how to solve this problem but nothing worked, my app just kept crashing.
Here's the code for the simple chat program.
Server
public class server {
public static Map<Integer, MiniServer> clients;
public static void main(String args[]) throws IOException {
clients = new HashMap<>();
boolean listeningSocket = true;
ServerSocket serverSocket = new ServerSocket(1234);
while (listeningSocket) {
Socket socket = serverSocket.accept();
MiniServer mini = new MiniServer(socket);
if (clients.isEmpty()) {
clients.put(1, mini);
mini.setId(1);
} else {
int i = 1;
while (clients.containsKey(i))
i++;
clients.put(i, mini);
mini.setId(i);
}
mini.start();
}
serverSocket.close();
}
Client
public class client {
private static String message;
private static boolean connected;
private static boolean connectedInternet;
public static void main(String args[]) throws UnknownHostException, IOException {
Scanner textReader = new Scanner(System.in);
Socket socket = new Socket("127.0.0.1", 1234);
Scanner inputStreamReader = new Scanner(socket.getInputStream());
connectedInternet = true;
System.out.println("Hello Stranger, get ready to chat.");
PrintStream printStream = new PrintStream(socket.getOutputStream());
Thread getMessage = new Thread() {
public void run() {
while (true) {
message = textReader.nextLine();
if (!connected)
System.out.println("You are not connected to another Stranger yet, please wait.");
else
printStream.println(message);
}
}
};
getMessage.start();
while (connectedInternet) {
String temp = inputStreamReader.nextLine();
if (temp.equals("connected")) {
connected = true;
System.out.println("Found a Stranger, say hey !");
} else if (connected) {
if (temp.equals("!close")) {
System.out.println("Stranger disconnected.");
printStream.println("!new");
} else
System.out.println("Stranger: " + temp);
}
}
textReader.close();
socket.close();
inputStreamReader.close();
}
MiniServer
public class MiniServer extends Thread {
private Socket socket = null;
public int id;
private boolean foundPlayer;
private int colleague;
private boolean connected;
public MiniServer(Socket socket) {
super("MiniServer");
this.socket = socket;
}
public void run() {
Scanner inputStreamReader = null;
String message;
try {
inputStreamReader = new Scanner(socket.getInputStream());
} catch (IOException e) {
e.printStackTrace();
}
PrintStream p = null;
try {
p = new PrintStream(socket.getOutputStream());
} catch (IOException e) {
e.printStackTrace();
}
List<Integer> keys = new ArrayList<Integer>(server.clients.keySet());
while (!foundPlayer) {
for (Integer key : keys) {
if (!server.clients.get(key).foundPlayer && key != id) {
server.clients.get(key).foundPlayer = true;
foundPlayer = true;
server.clients.get(key).colleague = id;
colleague = server.clients.get(key).id;
}
}
try {
keys = new ArrayList<Integer>(server.clients.keySet());
} catch (ConcurrentModificationException e) {
}
}
p.println("connected");
connected = true;
while (connected) {
try {
message = inputStreamReader.nextLine();
if (message.equals("!new")) {
foundPlayer = false;
keys = new ArrayList<Integer>(server.clients.keySet());
while (!foundPlayer) {
for (Integer key : keys) {
if (!server.clients.get(key).foundPlayer && key != id) {
server.clients.get(key).foundPlayer = true;
foundPlayer = true;
server.clients.get(key).colleague = id;
colleague = server.clients.get(key).id;
}
}
try {
keys = new ArrayList<Integer>(server.clients.keySet());
} catch (ConcurrentModificationException e) {
}
}
p.println("connected");
} else
sendToClient(message);
} catch (NoSuchElementException e) {
server.clients.remove(id);
sendToClient("!close");
closeSocket();
connected = false;
}
}
}
public void setId(int i) {
id = i;
}
public void sendToClient(String message) {
Socket colleagueSocket = server.clients.get(colleague).socket;
PrintStream rr = null;
try {
rr = new PrintStream(colleagueSocket.getOutputStream());
} catch (IOException e) {
e.printStackTrace();
}
rr.println(message);
}
public void closeSocket() {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
This program works great, but I'm pretty sure there are tons of problems with it.
Now here's my Server-side code for my android application.
Server
public class Server {
public static Map<Integer, MiniServer> clients;
public static void main(String args[]) throws IOException {
clients = new HashMap<>();
boolean listeningSocket = true;
ServerSocket serverSocket = new ServerSocket(1234);
while (listeningSocket) {
Socket socket = serverSocket.accept();
MiniServer mini = new MiniServer(socket);
if (clients.isEmpty()) {
clients.put(1, mini);
mini.setId(1);
} else {
int i = 1;
while (clients.containsKey(i))
i++;
clients.put(i, mini);
mini.setId(i);
}
mini.start();
}
serverSocket.close();
}
Mini Server
public class MiniServer extends Thread {
private Socket socket;
private Socket colleagueSocket;
public int id;
private boolean foundPlayer;
private int colleague;
private boolean connected;
private String crossOrCircle;
private boolean thisGoes;
private Thread timeOut;
private PrintStream p;
private Timer timer;
public MiniServer(Socket socket) {
super("MiniServer");
this.socket = socket;
}
public void run() {
Scanner inputStreamReader = null;
String message;
try {
inputStreamReader = new Scanner(socket.getInputStream());
} catch (IOException e) {
e.printStackTrace();
}
try {
p = new PrintStream(socket.getOutputStream());
} catch (IOException e) {
e.printStackTrace();
}
List<Integer> keys = new ArrayList<Integer>(Server.clients.keySet());
while (!foundPlayer) {
for (Integer key : keys) {
if (!Server.clients.get(key).foundPlayer && key != id) {
Server.clients.get(key).foundPlayer = true;
foundPlayer = true;
Server.clients.get(key).colleague = id;
colleague = Server.clients.get(key).id;
crossOrCircle = "X";
Server.clients.get(key).crossOrCircle = "O";
thisGoes = true;
Server.clients.get(key).thisGoes = false;
colleagueSocket=Server.clients.get(key).colleagueSocket;
Server.clients.get(key).colleagueSocket=socket;
}
}
try {
keys = new ArrayList<Integer>(Server.clients.keySet());
} catch (ConcurrentModificationException e) {
}
}
p.println("connected");
connected = true;
p.println(crossOrCircle);
while (connected) {
try {
message = inputStreamReader.nextLine();
if (Character.toString(message.charAt(0)).equals(crossOrCircle) && thisGoes) {
p.println(message);
sendToClient(message);
thisGoes = false;
Server.clients.get(colleague).thisGoes = true;
} else if (message.equals("!close")) {
sendToClient("!closeClient");
p.println("!closeClient");
Server.clients.get(colleague).connected = false;
connected = false;
Server.clients.get(colleague).closeSocket();
closeSocket();
Server.clients.remove(colleague);
Server.clients.remove(id);
} else if (message.equals("!pause")) {
timeOut = new Thread() {
#Override
public void run() {
timer = new Timer();
timer.schedule(
new TimerTask() {
#Override
public void run() {
sendToClient("!closeClient");
p.println("!closeClient");
Server.clients.get(colleague).connected = false;
connected = false;
Server.clients.get(colleague).closeSocket();
closeSocket();
Server.clients.remove(colleague);
Server.clients.remove(id);
}
},
5000
);
}
};
timeOut.start();
} else if (message.equals("!resume")) {
timer.cancel();
}
} catch (NoSuchElementException e) {
sendToClient("!closeClient");
p.println("!closeClient");
Server.clients.get(colleague).connected = false;
connected = false;
Server.clients.get(colleague).closeSocket();
closeSocket();
Server.clients.remove(colleague);
Server.clients.remove(id);
}
}
}
public void setId(int i) {
id = i;
}
public void sendToClient(String message) {
PrintStream rr = null;
try {
rr = new PrintStream(colleagueSocket.getOutputStream());
} catch (IOException | NullPointerException e) {
e.printStackTrace();
}
rr.println(message);
}
public void closeSocket() {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
public Socket getSocket(){
return this.socket;
}
There's a problem in the sendClient() method, it keeps throwing NullPointerException.
What can I do? I'm not asking you to solve my problem.
Could you give me some advices please?
Thank you very much :)
Edit:
I forgot to mention some thing- I'm running the server on my computer and I'm using two different devices that are connected to the LAN.
java.lang.NullPointerException
at com.ilya.rabinovich.tictactoe.MiniServer.sendToClient(MiniServer.java:134)
at com.ilya.rabinovich.tictactoe.MiniServer.run(MiniServer.java:75)
Exception in thread "MiniServer" java.lang.NullPointerException
at com.ilya.rabinovich.tictactoe.MiniServer.sendToClient(MiniServer.java:138)
at com.ilya.rabinovich.tictactoe.MiniServer.run(MiniServer.java:75)
Edit 2:
I fixed this exception by changing this line
colleagueSocket=Server.clients.get(key).colleagueSocket;
To
colleagueSocket=Server.clients.get(key).socket;
When running this app on the android emulators (android studio) it works perfectly fine, but when I try running this app on external devices (Lg g3 and nexus 7) it works really weird and crashes most of the times.
Edit 3:
Okay I solved the problem =)
The problem was in the client(runOnUiThread).
Anyways, do you think there are ways to improve my Server code? Thanks !
I don't know if you already did, but you need to whitelist the server ip in your config.xml file.
This might be one one reason.
I have this Server class,
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
public class Server {
public static ArrayList<String> waiting = new ArrayList<String>();
public static ArrayList<String> playing = new ArrayList<String>();
public static ArrayList<Integer> score = new ArrayList<Integer>();
public static void main(String[] args) {
try {
ServerSocket server = new ServerSocket(4321);
while (true) {
try {
Socket socket = server.accept();
new EchoThread(socket).start();
} catch (Exception exc) {
exc.printStackTrace();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
public void addClient(String name) {
waiting.add(name);
}
public int getNumClients() {
return waiting.size();
}
public String getClientName(int i) {
return waiting.get(i);
}
public void play() {
int scr = 0;
for (int i = 0; i < 4; i++) {
playing.add(waiting.get(0));
score.add(scr);
waiting.remove(0);
}
}
public boolean checkIfPlaying(String name) {
if (playing.indexOf(name) >= 0) {
return true;
} else {
return false;
}
}
}
and the Thread Class,
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
public class EchoThread extends Thread {
protected Socket socket;
public EchoThread(Socket clientSocket) {
this.socket = clientSocket;
}
public void run() {
Server s = new Server();
DataInputStream in = null;
DataOutputStream out = null;
String line;
try {
in = new DataInputStream(socket.getInputStream());
out = new DataOutputStream(socket.getOutputStream());
} catch (IOException e) {
return;
}
while (true) {
try {
line = in.readLine();
String[] prot = line.split(":");
if (prot[0].equals("/login")) {
s.addClient(prot[1]);
} else if (prot[0].equals("/waiting")) {
if (s.checkIfPlaying(prot[1])) {
out.writeBytes("Playing" + "\r\n");
} else {
if (s.getNumClients() >= 4) {
s.play();
out.writeBytes("Playing" + "\r\n");
} else {
out.writeBytes(s.getNumClients() + "\r\n");
}
}
}
} catch (IOException e) {
e.printStackTrace();
return;
}
}
}
}
If the client connect to the server, the name of the client is stored in Server Class Array, waiting.
If the waiting clients is equals to 4, it will remove from the waiting array and put it in playing array.
I would like to make the server send message to the first 4 clients in playing array.
How can I do it?
For your Server Class, I would change your ArrayList< String > for waiting and playing to ArrayList< EchoThread >. This way your Server class is tracking each client object themselves instead of just their names. When you instantiate your EchoThread objects, I would pass the local server object to each EchoThread that way each object knows about the server that instantiated them.
Server Class
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
public class Server {
public ArrayList<EchoThread> waiting = new ArrayList<EchoThread>();
public ArrayList<EchoThread> playing = new ArrayList<EchoThread>();
public ArrayList<Integer> score = new ArrayList<Integer>();
public static void main(String[] args) {
try {
// Instantiate a single server object that you can pass into your connected clients
Server myServer = new Server();
ServerSocket server = new ServerSocket(4321);
while (true) {
try {
Socket socket = server.accept();
// Pass myServer into Echo Thread
new EchoThread(myServer, socket).start();
} catch (Exception exc) {
exc.printStackTrace();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
// Have to synchronize this since multiple clients could be adding to this list at the same time
public synchronized void addClient(EchoThread client) {
waiting.add(client);
}
public int getNumClients() {
return waiting.size();
}
public String getClientName(int i) {
return waiting.get(i).getCName();
}
public void play() {
int scr = 0;
for (int i = 0; i < 4; i++) {
EchoThread clientBeingMovedToPlaying = waiting.get(0);
playing.add(clientBeingMovedToPlaying);
score.add(scr);
waiting.remove(0);
// This will be a new method in your EchoThread class
clientBeingMovedToPlaying.SendServerPlayingMessage();
}
}
public boolean checkIfPlaying(String name) {
boolean isPlaying = false;
for(EchoThread client : playing) {
if (client.getName().contentEquals(name)) {
isPlaying = true;
break;
}
}
return isPlaying;
}
}
For your Echo Thread class, I would make your variables in your run method class variables so they can be used throughout the class
EchoThread Class
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
public class EchoThread extends Thread {
protected Socket socket;
protected Server s;
protected DataInputStream in;
protected DataOutputStream out;
protected String line;
protected String clientName;
// This way, each EchoThread object knows about the server
public EchoThread(Server theServer, Socket clientSocket) {
this.s = theServer;
this.socket = clientSocket;
}
public void run() {
try {
in = new DataInputStream(socket.getInputStream());
out = new DataOutputStream(socket.getOutputStream());
} catch (IOException e) {
return;
}
while (true) {
try {
line = in.readLine();
String[] prot = line.split(":");
if (prot[0].equals("/login")) {
// Original code
//s.addClient(prot[1]);
// New code
clientName = prot[1];
s.addClient(this);
} else if (prot[0].equals("/waiting")) {
if (s.checkIfPlaying(prot[1])) {
out.writeBytes("Playing" + "\r\n");
} else {
// You don't want multiple clients firing the play method, so you need to synchronize your server object
synchronized (s) {
if (s.getNumClients() >= 4) {
s.play();
out.writeBytes("Playing" + "\r\n");
} else {
out.writeBytes(s.getNumClients() + "\r\n");
}
}
}
}
} catch (IOException e) {
e.printStackTrace();
return;
}
}
}
public String getCName() {
return clientName;
}
public void SendServerPlayingMessage() {
if (out != null) {
// Send whatever message you want
}
}
}
I think this'll get you what your wanting... Forgive any syntax or logical errors, I don't have an IDE right in front of me at the moment.
I have a slight problem, I have a TCP class which connects to a server, transfers data then closes, this all works well except for if I connect, then stop it, it works, if I keep on doing this, it works, but on the fifth time the connection hangs without any error and doesn't transfer any data.. I've got no idea how to fix this... This is my TCP class code:
package com.millennium.isynccrm.Classes;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import android.os.AsyncTask;
import android.os.CountDownTimer;
import android.util.Log;
public class TcpClient {
public static boolean connected = false;
private static Socket socket;
private static boolean pause = false;
private static SyncClient syncClient = new SyncClient();
public static int sendCount = 0;
public static int receiveCount = 0;
private static AsyncTask<?, ?, ?> sendAsyncTask;
private static AsyncTask<?, ?, ?> receiveAsyncTask;
public TcpClient() { }
public void send (String line) {
if (!connected) connect();
while (!connected) { }
sendAsyncTask = new SenderThread().execute(line);
}
public void disconnect() {
try {
if(connected == true) {
socket.close();
connected = false;
sendCount = 0;
receiveCount = 0;
if (receiveAsyncTask.getStatus().name().equals("RUNNING")) {
receiveAsyncTask.cancel(true);
}
if (sendAsyncTask.getStatus().name().equals("RUNNING")) {
sendAsyncTask.cancel(true);
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
public void pauseReceivingForTimeInterval(int milliseconds) {
pause = true;
new CountDownTimer(milliseconds, 0) {
public void onTick(long millisUntilFinished) { }
public void onFinish() {
pause = false;
}
}.start();
}
private void connect() {
new Thread(new Runnable() {
public void run() {
try {
if (connected == false) {
socket = new Socket("192.168.1.1", 80);
connected = true;
sendCount = 0;
receiveCount = 0;
try {
if (receiveAsyncTask.getStatus().name().equals("FINISHED")) {
receiveAsyncTask = new RecieverThread().execute("");
} else if (receiveAsyncTask.getStatus().name().equals("RUNNING")) {
receiveAsyncTask.cancel(true);
receiveAsyncTask = new RecieverThread().execute("");
}
} catch (Exception e) { receiveAsyncTask = new RecieverThread().execute(""); }
}
} catch (UnknownHostException e) {
connected = false;
e.printStackTrace();
} catch (IOException e) {
connected = false;
e.printStackTrace();
}
}
}).start();
}
private static PrintWriter output;
private static BufferedReader input = null;
private class RecieverThread extends AsyncTask<String, Void, String> {
protected String doInBackground(String... line) {
while (pause) { }
try {
receiveCount++;
if (receiveCount == 1) input = new BufferedReader(new InputStreamReader(socket.getInputStream()), 8 * 1024);
return input.readLine();
} catch (IOException e) {
Log.d("error", "stop");
}
return "stop";
}
protected void onPostExecute(String result) {
if (result == null) return;
else if (!result.equals("") && !result.equals("stop")) syncClient.recieveMessage(result);
else if (!result.equals("stop")) receiveAsyncTask = new RecieverThread().execute("");
}
}
private class SenderThread extends AsyncTask<String, Void, String> {
protected String doInBackground(String... line) {
while (pause) { }
sendCount++;
if (sendCount == 1) {
try {
output = new PrintWriter(socket.getOutputStream(),true);
} catch(Exception e) { e.printStackTrace(); }
}
String msg = line[0] + "\r\n";
output.print(msg);
output.flush();
return "";
}
protected void onPostExecute(String result) {
}
}
}
As you can see another class sends a line to this class to send to the server, then a Async task sends it and another Async task receives it and passes it onto another class which processes it and so on. On the UI I have a start button which when is pressed turns into a stop button and when stop is pressed it calls the 'disconnect' function in here.
I'm not too sure wherever I have done my RecieverThread AsyncTask is correct, it waits for a line from the socket then passes it on and restarts it self to listen for another line, is this a 'good' way of doing this? Or is it a terrible way (which I imagine it is). To be honest I think this class is very 'messy' and I will more than likely be redoing it.
Any suggestion why I can never send data on the fifth time I connect to the server? (One last note, the server is not to blame here, as we have a iPhone app which does the same thing) (Extra side note.. I'm pretty new to Tcp connections and that sort of stuff, and new to Threading/Async Tasks.) :)
Any help, assistance would be much appreciated (: Thanks!
while (!connected) {}??? that's no way to do asynchronous anything. You are hogging the CPU waiting for something to happen, and preventing it from happening by hogging the CPU. Use a Selector, or do a blocking-mode connect.