This may be a stupid question, but here goes.
Im writing this chat program, where there is a server, and clients that can connect to it. I want to implement private messaging into the program, but I don't know how to get the clients to directly connect to eachother. For the server, I used a ServerSocket, which runs on a single port. To get that to work, I needed to forward a port to the server. Is there a way to get the clients to wait for connections, without forwarding a port to them?
Thanks
The whole point of TCP/IP is that a single client connects to a predefined port on a server. So yes, you'll also need to have a ServerSocket on the client that's going to accept the direct connection. You'll almost always run into trouble with port forwarding and the like, which is why UPnP was invented one day.
What you are trying to do is 'peer to peer' connectivity, aka P2P, which is always, by its very definition, plagued by firewalling problems. As such it's usually, especially for a chat, easier to use the central server as 'switchboard' server and relay the private messages as well.
I've written not long time ago a template for multiple client - server application, that might help you to solve your problem. The rest of your question was already answerd by #Niels, I think ;)
import java.net.*;
import java.io.*;
class ServeConnection extends Thread {
private Socket socket = null;
private BufferedReader in = null;
private PrintWriter out = null;
public ServeConnection(Socket s) throws IOException {
// init connection with client
socket = s;
try {
in = new BufferedReader(new InputStreamReader(
this.socket.getInputStream()));
out = new PrintWriter(this.socket.getOutputStream(), true);
} catch (IOException e) {
System.err.println("Couldn't get I/O.");
System.exit(1);
}
start();
}
public void run() {
System.out.println("client accepted from: " + socket.getInetAddress()
+ ":" + socket.getPort());
// get commands from client, until is he communicating or until no error
// occurs
String inputLine, outputLine;
try {
while ((inputLine = in.readLine()) != null) {
System.out.println("request: " + inputLine);
outputLine = inputLine;
out.println("I've recived "+outputLine);
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("server ending");
out.close();
try {
in.close();
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
class Server {
public static void svr_main(int port) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(port);
} catch (IOException e) {
System.err.println("Could not listen on port: " + port);
System.exit(1);
}
System.out.println("Server ready");
try {
while (true) {
Socket socket = serverSocket.accept();
try {
new ServeConnection(socket);
} catch (IOException e) {
System.err.println("IO Exception");
}
}
} finally {
serverSocket.close();
}
}
}
class Client {
static Socket echoSocket = null;
static PrintWriter out = null;
static BufferedReader in = null;
public static void cli_main(int port, String servername) throws
IOException {
try {
echoSocket = new Socket(servername, port);
out = new PrintWriter(echoSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(
echoSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Don't know about host: " + servername);
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for " + servername);
System.exit(1);
}
System.out.println("Client ready!");
while (true) {
inputLine = (in.readLine().toString());
if (inputLine == null) {
System.out.println("Client closing!");
break;
}
// get the input and tokenize it
String[] tokens = inputLine.split(" ");
}
out.close();
in.close();
echoSocket.close();
System.out.println("Client closing");
}
}
public class MyClientServerSnippet{
public static void main(String[] args) throws IOException {
if (args.length == 0) {
System.err.println("Client: java snippet.MyClientServerSnippet<hostname> <port>");
System.err.println("Server: java snippet.MyClientServerSnippet<port>");
System.exit(1);
}
else if (args.length > 1) {
System.out.println("Starting client...\n");
Client client = new Client();
client.cli_main(3049, "127.0.0.1");
} else {
System.out.println("Starting server...\n");
Server server = new Server();
server.svr_main(3049);
}
}
}
Related
I'm trying to make a TCP listener on java. The software should act like "Hercules" or SocketTest. Problem is, it's not recieving any connections from other computers or devices. It does connect to Hercules or SocketTest but not to my program.
public class Server3 {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
System.out.println(InetAddress.getLocalHost());
serverSocket = new ServerSocket(7165,0,InetAddress.getLocalHost());
} catch (IOException e) {
System.err.println("Could not listen on port: 7165.");
System.exit(1);
}
Socket clientSocket = null;
try {
clientSocket = serverSocket.accept();
System.out.println("Client connected!");
System.out.println(clientSocket.getRemoteSocketAddress()+" connected\n");
} catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
}
clientSocket.setSoTimeout(1000);
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(
clientSocket.getInputStream()));
String inputLine ;
boolean connected = true;
while (connected)
{
try {
inputLine = in.readLine();
System.out.println("Client said : "+inputLine);
if (inputLine == null)
{
System.out.println("Client Disconnected!");
connected = false;
}
}
catch(java.net.SocketTimeoutException e)
{
System.out.println("Timed out trying to read from socket");
}
}
out.close();
in.close();
clientSocket.close();
serverSocket.close();
}
I also used ServerSocket socket = new ServerSocket(port) but no results.
Is there any configurations to do more than just port ? Is it even possible to make this?
I'm creating an update client via Sockets and I'm getting a Broken Pipe on the server side. The server accepts a client socket and responds to the same socket with either a message or a large byte array (~180MB). The error does not happen when testing locally (both client and server on the same machine) and it seems that it happens while sending the byte array. I'm not specifying a time out on the client socket and don't know why it is closing before reading the full response. Its my first time working with sockets and any help would be appreciated.
My Client Socket Code:
public static Response makeRequest(Request req) throws IOException {
Response response = null;
Socket echoSocket = null;
ObjectOutputStream out = null;
ObjectInputStream in = null;
echoSocket = new Socket(serverHost, 10008);
out = new ObjectOutputStream(echoSocket.getOutputStream());
in = new ObjectInputStream(
echoSocket.getInputStream());
BufferedReader stdIn = new BufferedReader(
new InputStreamReader(System.in));
out.writeObject(req);
try {
response = (Response)in.readObject();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
out.close();
in.close();
stdIn.close();
echoSocket.close();
return response;
}
Response is just a POJO holding the response (string/byte[] and other data)
My Server Code (copied an example of Sun/Oracle site and added my code to it)
public class Server extends Thread {
private Socket clientSocket;
public Server(Socket clientSocket) {
this.clientSocket = clientSocket;
start();
}
public void run()
{
{
System.out.println ("New Communication Thread Started");
try {
ObjectOutputStream out = new ObjectOutputStream(clientSocket.getOutputStream());
ObjectInputStream in = new ObjectInputStream(clientSocket.getInputStream());
Request request = null;
try {
request = (Request)in.readObject();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
UpdateDAO dao = new UpdateDAO();
ClientDAO cdao = new ClientDAO();
Update update = null;
Client client = null;
Session s = HibernateUtil.currentSession();
Transaction t = s.beginTransaction();
if (request != null) {
client = cdao.getClient(request.getClientId());
LogItem log = new LogItem();
log.setClient(client);
log.setTimestamp(new Date());
log.setAction(request.getAction());
if (request.getResponse() != null) {
update = dao.getUpdate(request.getResponse().getUpdateId());
}
TaskContext ctx = new TaskContext(request, client, update, log);
System.out.println("Action: " + request.getAction().getDescription());
Task task = TaskFactory.getTask(request.getAction());
System.out.println(task.getClass().getName());
Response response = task.perform(ctx);
out.writeObject(response);
log.setClientTaskDescription(request.getMessage());
log.setUpdate(ctx.getUpdate());
dao.save(ctx.getLog());
if (ctx.getUpdate() != null) {
dao.update(ctx.getUpdate());
}
} else {
out.writeObject(new Response("what"));
}
t.commit();
out.close();
in.close();
clientSocket.close();
}
catch (IOException e)
{
e.printStackTrace();
System.exit(1);
}
}
}
public static void main(String[] args) throws IOException
{
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(10008);
System.out.println ("Connection Socket Created");
try {
while (true)
{
System.out.println ("Waiting for Connection");
new Server (serverSocket.accept());
}
}
catch (IOException e)
{
System.err.println("Accept failed.");
System.exit(1);
}
}
catch (IOException e)
{
System.err.println("Could not listen on port: 10008.");
System.exit(1);
}
finally
{
try {
serverSocket.close();
}
catch (IOException e)
{
System.err.println("Could not close port: 10008.");
System.exit(1);
}
}
}
}
If the client is, in fact, running out of memory:
java -Xmx512m -jar <the jar>
or
java -Xmx512m com.foo.blah.YourClass
would increase the maximum heap for the client/server. Keep in mind you may have to increase the heap for both sides of the pipe since both sides would be reading all ~180mb into memory at runtime.
I am trying to write a small socket program with client side in groovy and the server side in Java. Below is the code I wrote
client:
def s = new Socket("localhost", 4444);
s << "Server before withStreams\n";
s.withStreams { input, output ->
println"Sending message1"
output << "server message1\n"
}
s.close();
server:
import java.io.*;
import java.net.*;
public class Logger{
ServerSocket providerSocket;
Socket connection = null;
BufferedReader in;
String message="InitialMessage";
Logger(){}
void run()
{
try{
providerSocket = new ServerSocket(4444, 10);
try{
Thread.sleep(1000);
}
catch(InterruptedException ie)
{
System.out.println("Sleep Interrupted");
}
System.out.println("Waiting for connection");
connection = providerSocket.accept();
System.out.println("Connection received from " + connection.getInetAddress().getHostName());
in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
do{
if(in.ready())
{
try{
System.out.println(in.read());
message = in.readLine();
System.out.println("client>" + message);
}
catch(IOException e)
{
System.out.println(e);
e.printStackTrace();
break;
}
}
} while(!message.equals("bye"));
}
catch(IOException ioException){
ioException.printStackTrace();
}
finally{
//4: Closing connection
try{
in.close();
providerSocket.close();
}
catch(IOException ioException){
ioException.printStackTrace();
}
}
}
public static void main(String args[])
{
Logger server = new Logger();
while(true){
server.run();
}
}
}
When I execute both programs, Socket communication is established. But I get a IOException in server code when it reads from the socket (message = in.readLine();)
I guess there is some format problem in writing into socket in client. But not able to figure out the exact problem. Can anybody help?
You generally don't want to close your ServetSocket for each client connection. You want to do this once (or every time you start the server) then on each accept() handle the client connection and close the socket for that connection but keep the ServerSocket open until you want to stop the server.
Here's a rewritten version of your example server that also creates a new Thread for each client request to handle multiple concurrent requests. Note that since the test client doesn't send the terminating string "bye" the connection and socket stays open.
import java.io.*;
import java.net.*;
public class Logger {
private ServerSocket providerSocket;
Logger() {
}
public void start() {
try {
providerSocket = new ServerSocket(4444, 10);
while (true) {
System.out.println("Waiting for connection");
Socket connection = providerSocket.accept();
new Thread(new Job(connection)).start();
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (providerSocket != null) {
System.out.println("Stopping server");
try {
providerSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
static class Job implements Runnable {
final Socket connection;
private static int id;
private int clientId = ++id;
public Job(Socket connection) {
this.connection = connection;
}
public void run() {
BufferedReader in = null;
try {
System.out.println("Connection " + clientId + " received from " + connection.getInetAddress().getHostName());
in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String message = "InitialMessage";
do {
if (in.ready()) {
try {
// not sure why want to read one character then read the line
//int ch = in.read();
//System.out.println(ch);
// -1 if the end of the stream has been reached
//if (ch == -1) break;
message = in.readLine();
// null if the end of the stream has been reached
if (message == null) break;
System.out.println("client>" + message);
} catch (IOException e) {
System.out.println(e);
e.printStackTrace();
break;
}
}
} while (!message.equals("bye"));
} catch (IOException e) {
e.printStackTrace();
} finally {
//4: Closing connection
System.out.println("Close connection " + clientId);
if (in != null)
try {
in.close();
} catch (IOException ioException) {
ioException.printStackTrace();
}
try {
connection.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
public static void main(String args[]) {
Logger server = new Logger();
server.start();
}
}
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
how to do ssl socket programming
I am doing communication from android as client and laptop as server through Socket using wireless router.But how if i want to do communication securely. here is my android code in eclipse
public class TCPClient implements Runnable {
public void run() {
try {
InetAddress serverAddr = InetAddress.getByName("192.168.1.2");
Log.d("TCP", "C: Connecting...");
Socket socket = new Socket(serverAddr,12345);
String message = "Hello from Client android emulator";
try {
Log.d("TCP", "C: Sending: '" + message + "'");
PrintWriter out = new PrintWriter( new BufferedWriter( new OutputStreamWriter(socket.getOutputStream())),true);
out.println(message);
Log.d("TCP", "C: Sent.");
Log.d("TCP", "C: Done.");
} catch(Exception e) {
Log.e("TCP", "S: Error", e);
} finally {
socket.close();
}
} catch (Exception e) {
Log.e("TCP", "C: Error", e);
}
}
}
here is server code in Netbean that is working and communicating with android. what changes i have to do ?
public class TCPDesktopServer implements Runnable{
public static final String SERVERIP = "10.0.2.15";
public static final int SERVERPORT = 12345;
public void run() {
try {
System.out.println("S: Connecting...");
ServerSocket serverSocket = new ServerSocket(SERVERPORT);
while (true) {
Socket client = serverSocket.accept();
System.out.println("S: Receiving...");
try {
BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
String str = in.readLine();
System.out.println("S: Received: '" + str + "'");
} catch(Exception e) {
System.out.println("S: Error");
e.printStackTrace();
} finally {
client.close();
System.out.println("S: Done.");
}
}
} catch (Exception e) {
System.out.println("S: Error");
e.printStackTrace();
}
}
public static void main (String a[]) {
Thread desktopServerThread = new Thread(new TCPDesktopServer());
desktopServerThread.start();
}
}
Seems like you need to use javax.crypto.CipherOutputStream/CipherInputStream, or if you want a more standardized approach you could try Apache commons (http://commons.apache.org/) where there is a basic implementation of SSL.
You could very easily use the SSLSocket class which is part of the base java distribution. If you are having problems getting certificates to validate, you can user this tutorial to show you how to allow self-signed certs and non-matching host names.
I have a problem with my Java program. It has a socket connection between a server and many client. Here is the server (the part which concerns the problem):
private static ArrayList<ParallelServer> clientConnected = new ArrayList<ParallelServer>();
public Server(int port) {
this.port = port;
if (!startServer())
JOptionPane.showMessageDialog(new JFrame(""),
"Error!", "ERROR!",
JOptionPane.ERROR_MESSAGE);
}
private boolean startServer() {
try {
server = new ServerSocket(port);
loadDatabase();
} catch (IOException ex) {
ex.printStackTrace();
return false;
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
return true;
}
public void runServer() {
while (true) {
try {
client = server.accept();
ParallelServer pServer = new ParallelServer(client);
clientConnected.add(pServer);
Thread thread = new Thread(pServer);
thread.start();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
public static void sendBroadcast(String username) throws IOException {
for(int i = 0; i < clientConnected.size(); i++)
clientConnected.get(i).sendAnswer("#change," + username);
}
The parallel server is:
private Socket client;
private InputStreamReader inputstreamreader;
private BufferedReader bufferedreader;
private PrintWriter printwriter;
public ParallelServer(Socket client) {
this.client = client;
}
public void run() {
try {
inputstreamreader = new InputStreamReader(client.getInputStream());
bufferedreader = new BufferedReader(inputstreamreader);
printwriter = new PrintWriter(client.getOutputStream(), true);
String lineread = "";
while (client.isConnected()) {
lineread = bufferedreader.readLine();
doCommand(lineread);
}
} catch (UnknownHostException unhe) {
} catch (InterruptedIOException intioe) {
} catch (IOException ioe) {
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
public void sendAnswer(String answer) throws IOException {
printwriter = new PrintWriter(client.getOutputStream(), true);
printwriter.println(answer);
printwriter.flush();
}
And here is the client:
private String serverurl = "localhost";
private int serverport = 7777;
private PrintWriter printwriter;
private InputStreamReader inputstreamreader;
private BufferedReader bufferedreader;
private Socket server;
public Client() {
server = null;
try {
server = new Socket(serverurl, serverport);
server.setSoTimeout(5000);
} catch (UnknownHostException unhe) {
System.out.println("UnknownHostException: " + unhe.getMessage());
} catch (InterruptedIOException intioe) {
System.out.println("Timeout while attempting to establish socket connection.");
} catch (IOException ioe) {
JOptionPane.showMessageDialog(new JFrame(),"Unable to reach the server!","ERROE!",JOptionPane.ERROR_MESSAGE);
}
}
public String sendCommand(String command) throws IOException {
if(server == null) {
try {
server = new Socket(serverurl, serverport);
server.setSoTimeout(5000);
} catch (UnknownHostException unhe) {
System.out.println("UnknownHostException: " + unhe.getMessage());
} catch (InterruptedIOException intioe) {
System.out.println("Timeout while attempting to establish socket connection.");
} catch (IOException ioe) {
JOptionPane.showMessageDialog(new JFrame(),"Unable to reach the server!","ERROR!",JOptionPane.ERROR_MESSAGE);
}
}
if(server != null) {
printwriter = new PrintWriter(server.getOutputStream(), true);
printwriter.println(command);
printwriter.flush();
inputstreamreader = new InputStreamReader(server.getInputStream());
bufferedreader = new BufferedReader(inputstreamreader);
return bufferedreader.readLine();
}
else
return "#serverProblem";
}
The program is a simple online game with turns. Players' turns are created with a queue and when a player passes his turn, the server send a broadcast message which say "Now it is 'Player 1' turn." (for instance). My problem is that when a client receive the message, its like it add the answer "Now it is 'Player 1' turn." to the next message it will receive. In my case: when a player passes his turn, he sends "#passTurn,username". The ParallelServer class polls it from the queue, puts it at the bottom of the queue, sends the client "#ok" to tell it that the turn has changed successfully and tells the Server class to send the broadcast message. Then, when the same client will try do do a further action, it will consider "Now it is 'Player 1' turn." as the answer the server has given to it. Instead, I would like that the server and the clients work as always and when the broadcast message is cought, the client is notified without any collateral effect.
What can I do?
Thanks.
Your bi-directional message passing mechanism should look something like this:
Server:
Wait on any client InputStream
if (broadcast)
broadcast_message()
else
process_message()
Client:
Receiving Thread:
Wait on server broadcast
Sending Thread:
Wait on messages to be sent to server from the User Input
This should do the trick :)
Hope it helps. Cheers!