I'm working on a project that will require ea p2p server, but I haven't found any java-client php-server example code. I understand the concept of how udp hole punching works but I can't get anything to work in code.
What I've tried:
TheSocket.java
public class TheSocket {
public static String response = "hello";
public static String request;
public static String webServerAddress;
public static ServerSocket s;
protected static ServerSocket getServerSocket(int port)throws Exception{
return new ServerSocket(port);
}
public static void handleRequest(Socket s){
BufferedReader is;
PrintWriter os;
try{
webServerAddress = s.getInetAddress().toString();
is = new BufferedReader(new InputStreamReader(s.getInputStream()));
request = is.readLine();
System.out.println(request);
os = new PrintWriter(s.getOutputStream(), true);
os.println("HTTP/1.0 200");
os.println("Content-type: text/html");
os.println("Server-name: TheSocket");
os.println("Content-length: " + response.length());
os.println("");
os.println(response);
os.flush();
os.close();
s.close();
}catch(Exception e){
System.out.println("Failed to send response to client: " + e.getMessage());
}finally{
if(s != null){
try{
s.close();
}catch(Exception e){
e.printStackTrace();
}
}
}
return;
}
}
Main.java
public class Main {
public static void main(String[] args)throws Exception{
TheSocket.s = TheSocket.getServerSocket(6789);
while(true){
Socket serverSocket = TheSocket.s.accept();
TheSocket.handleRequest(serverSocket);
}
}
PHP-CONNECT.php - to get the other users port, I manually connect and use the port shown on webpage.
<?php
echo $_SERVER['REMOTE_ADDR'].':'.$_SERVER['REMOTE_PORT'];
?>
The issue with the code above, is that it cant make it to the socket unless I port forward.
Comment if you have any questions!
I was facing a similar problem. And was trying to solve it in a similar way.
Some parts of your code look wrong to me.
Sockets in Java are made for TCP but the title says UDP. Therefore u should use DatagramSockets.
But then we come to the point where i stuck too. HTTP-Requests use tcp as well, so opening the port with HTTP might lead to a corrupt port, after tcp session was closed. (Just a guess)
public class Main {
public static void main(String[] args) {
try
{
String httpRequest = "GET /index.php HTTP/1.1\n" +
"Host: <PHP SERVER NAME HERE>";
InetAddress IPAddress = InetAddress.getByName(<PHP SERVER IP HERE>);
DatagramSocket clientSocket = new DatagramSocket();
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
String sentence = httpRequest;
sendData = sentence.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 80);
clientSocket.send(sendPacket);
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(receivePacket);
String modifiedSentence = new String(receivePacket.getData());
System.out.println("FROM SERVER:" + modifiedSentence);
clientSocket.close();
}catch(Exception e){e.printStackTrace();}
}
}
The Code above theoretically sents a HTTP over UDP request. So that the displayed Port will be the UDP one. In my case i didnt get any response from the PHP Server and stuck at clientSocket.recieve(..) . I guess because the firewall of my webserver is blocking udp packets.
If the code works by anyone i would proceed like this:
save all accessing ips and ports to a DB and list them to the other client.
Write ur Data in DatagramPackets like above to the other client.
I hope this may help. If anyone can get it completly working i would also be interested in it :)
Related
I have a small task to send message from java to the following server (the server code is given by my teacher) all in LAN at my house:
Server (C#)
static void Main(string[] args)
{
var ipAddress = Dns.GetHostEntry("localhost").AddressList[0];
TcpListener server = new TcpListener(ipAddress, 25001);
server.Start();
// as long as we're not pending a cancellation, let's keep accepting requests
TcpClient client = server.AcceptTcpClient();
StreamReader clientIn = new StreamReader(client.GetStream());
string msg;
while ((msg = clientIn.ReadLine()) != null)
{
Console.WriteLine(msg);
}
}
I suspected that something is wrong with this server code, since I didn't succeeded to send it a message, but I succeeded to send to the following server message.
Client (Java):
try {
InetAddress serverAddr = InetAddress.getByName(serverIp);
Socket socket = new Socket(serverAddr, serverPort);
//sends the message to the server
PrintWriter mBufferOut = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);
Log.d(TAG, "Sending: " + message);
mBufferOut.println(message);
mBufferOut.flush();
socket.close();
}catch (Exception e){}
maybe it's because I can't send from to java client to c# server? or the teacher's code doesn't work well? I'm just wondering if the problem is in my code or in my teacher's code.
Hello stackoverflow community,
i am stuck at a problem regarding socket communication in Java.
Here is the sample code of my Server and Client class:
Server:
public class OTPServer {
static ServerSocket serverSocket;
final static int PORT = 4242;
static Socket clientConnection;
public static void main(String[] args) {
try {
serverSocket = new ServerSocket(PORT);
System.out.println("Socket initialized");
String serverMessage = "Hello, I am the Host";
ServerTool serverTool = new ServerTool();
while (true) {
clientConnection = serverSocket.accept();
if(clientConnection.isConnected()) {
System.out.println("Client connected");
}
BufferedReader clientInputReader = new BufferedReader(new InputStreamReader(clientConnection.getInputStream()));
DataOutputStream serverOutput = new DataOutputStream(clientConnection.getOutputStream());
System.out.println("Sending message to client: " + serverMessage);
serverOutput.writeBytes(serverTool.encodeMessage(serverMessage));
serverOutput.flush();
String clientMessage = clientInputReader.readLine();
System.out.println("Encoded answer from client: " + clientMessage);
String decodedMessage = serverTool.decodeMessage(clientMessage);
System.out.println("Decoded answer from client: " + decodedMessage);
serverOutput.close();
clientInputReader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("Hello, I am the OTP Server!");
}
Here is the Client:
public class OTPClient {
static Socket clientSocket;
final static int PORT = 4242;
final static String HOST = "localhost";
public static void main(String[] args) {
System.out.println("I am the OTP Client!");
String serverMessage;
String clientResponse = "I am the Client";
OTPTool otpTool = new OTPTool();
try {
clientSocket = new Socket(HOST, PORT);
BufferedReader serverInput = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
DataOutputStream outputStream = new DataOutputStream(clientSocket.getOutputStream());
System.out.println("Connection to Host established");
serverMessage = serverInput.readLine();
System.out.println("Encoded Message from Server: " + serverMessage);
String decodedMessage = otpTool.decodeMessage(serverMessage);
System.out.println("Decoded message from Server: " + decodedMessage);
System.out.println("Answering with own message: " + clientResponse);
outputStream.writeBytes(clientResponse);
outputStream.flush();
outputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
Now where is my problem:
The connection establishes and the Server seems to send its message to the client and waits for a answer. The Client does not print the message he got from the Server.
As soon as i cancel the Server the client prints the message it gets from the server as well as the information, that the answer is send end exits with exit code 0 so it seems that this part is fine it just is stuck somehow.
I already tried to flush the outputStream as you see in the example code given.
Is there something obvious im missing?
I know, this is really basic stuff but its my first time using sockets for communication.
Thank you in advance!
Best Regards,
Ronny
Btw: i know that the server only connects to one client requesting a connection. Thats absolutely sufficient for my use.
It is getting stuck because serverInput.readLine(); blocks until either a line break or end of file is encountered. On the server side, you are not sending a line break, so the client blocks.
I'm trying to communicate a Java program with a C# one but it's not working.
The code is really basic, here it is:
This is the Java client
static InetAddress ip;
static int port = 10000;
public static void main(String args[]) {
try {
ip = InetAddress.getByName("127.0.0.1");
DatagramSocket socket = new DatagramSocket(port, ip);
byte[] sendData = new byte[1024];
sendData = "Hola".getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, ip, port);
socket.send(sendPacket);
socket.close();
} catch (Exception e) {
}
}
And here it is the C# server
static UdpClient client;
static IPEndPoint sender;
void Start () {
byte[] data = new byte[1024];
string ip = "127.0.0.1";
int port = 10000;
client = new UdpClient(ip, port);
sender = new IPEndPoint(IPAddress.Parse(ip), port);
client.BeginReceive (new AsyncCallback(recibir), sender);
}
static void recibir(IAsyncResult res){
byte[] bResp = client.EndReceive(res, ref sender);
//Convert the data to a string
string mes = Encoding.UTF8.GetString(bResp);
//Display the string
Debug.Log(mes);
}
The c# server is a Unity file, I mean, I execute it from Unity, so Start is the first method called.
I would like them to communicate through port 10000 (or any ohter one) in my computer, java's main and c#'s start seem to be executed but the callback is never called.
Any ideas of why it isn't working? Thank you all.
BeginReceive() is non-blocking. Your program terminates before it can receive anything. Either use Receive() or put a busy-waiting-loop at the end of the server code.
I've solved it, in the Java client new DatagramSocket() must be called without any argument, and in the c# server new UdpClient(port); must be called only with the port.
I have the following Situation.
I have a Server class.
I have a Client class.
I have a MultiServerThread class.
When a Client connects to a Server, the Server creates a new MultiServerThread, which is processing the Input from the Client. That way I can have multiple Clients. So far so good.
The connection goes via TCP.
A short example:
Server class:
...
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
boolean listening = true;
try {
serverSocket = new ServerSocket(9999);
} catch (IOException e) {
System.err.println("Could not listen on port: " + serverSocket.getLocalPort() + ".");
System.exit(-1);
}
while (listening) {
new MultiServerThread(serverSocket.accept()).start();
}
serverSocket.close();
}
...
Client class:
...
public static void main(String[] args) throws IOException {
socket = new Socket(hostname, port);
out = new PrintWriter(socket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
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();
socket.close();
}
...
MultiServerThread class:
...
public MultiServerThread(Socket socket) throws SocketException {
super("MultiServerThread");
this.socket = socket;
// dSocket = new DatagramSocket(4445);
}
public void run() {
try {
PrintWriter myOutput = new PrintWriter(socket.getOutputStream(), true);
BufferedReader myInput = new BufferedReader(new InputStreamReader(socket.getInputStream()));
myOutput.println("Connected to client and ready to accept commands.");
while ((clientInput = myInput.readLine()) != null) {
//A SIMPLE LOGIN A USER
if (clientInput.contains("!login")) {
//save some string given by client into loggedUser
String loggedUser = clientInput.substring(7);
}
myOutput.close();
myInput.close();
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
What I need is:
I need to implement a notification that comes from a Server when for example the Username is "Bob". If the username is "Bob", the server should give a notification to the Client "Bob is here again!". In my project/homework this should be done with datagrams in Java.
So if the clientinput is "!login bob" then a datagram packet with the message ("Bob is here again!") should be sent to the client.
Question: Where exactly should I put the code of the Datagram request in? Can I put the datagram packet request into the MultiServerThread or into the Client?
It would be easier in the MultiServerThread because it already handles the !login.
Here:
if (clientInput.contains("!login")) {
//save some string given by client into loggedUser
String loggedUser = clientInput.substring(7);
//send datagram request to Server???
}
But this is going against the principle of networking?
you need to send the UDP port number to your client through the initial TCP connection. Then you start listening for UDP datagrams on your client on that port number. All other communications from server -> client will be on this udp socket. This is what your assignment suggests
I got it working ;-)
I definied a udp port in the thread and client class...
the client class got his port with arguments... it gave the udp Port to the thread... so both had the udp ports ;)
I am trying to write server to client program but I cannot communicate with the server in Java.
Here is the code block in my main.
InetAddress addr = InetAddress.getLocalHost();
ipAddress = "78.162.206.164";
ServerSocket serverSocket = new ServerSocket(0);
String randomStringForPlayerName = RandomStringGenerator.generateRandomString();
baseForReqOpp += ipAddress + " " + serverSocket + " " + randomStringForPlayerName;
Socket socket = new Socket(host,2050);
socket.setSoTimeout(100);
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out = new PrintWriter(socket.getOutputStream());
out.write(baseForReqOpp);
out.flush();
System.out.println(in.read());
I know that there is no problem in the server code and all the communication ports are ok.
But I cannot read anything from the server.
What can be the problem?
you have to create an output stream before the input stream
Here is some working code with communicating client and server sockets. Hopefully you can adapt it for your specific problem.
public class SocketTest {
public void runTest() {
try {
// create the server
new SimpleServer().start();
// connect and send a message
InetAddress addr = InetAddress.getLocalHost();
Socket sock = new Socket(addr, 9090);
ObjectOutputStream out = new ObjectOutputStream(sock.getOutputStream());
out.writeObject("Hello server");
out.flush();
ObjectInputStream in = new ObjectInputStream(sock.getInputStream());
System.out.println("from server: " + in.readObject());
sock.close();
} catch (Exception e) {
e.printStackTrace();
}
}
// server has to run in a separate thread so the code doesn't block
private class SimpleServer extends Thread {
#Override
public void run() {
try {
ServerSocket sock = new ServerSocket(9090);
Socket conn = sock.accept();
// the code blocks here until a client connects to the server
ObjectInputStream in = new ObjectInputStream(conn.getInputStream());
System.out.println("from client: " + in.readObject());
ObjectOutputStream out = new ObjectOutputStream(conn.getOutputStream());
out.writeObject("Hello client");
out.flush();
sock.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
To run it:
new SocketTest().runTest();
Your code will never work because you don't use threads. In order to start the server, you need to call accept at some point in your code
myServerSocket.accept();
this is a blocking call, ie the code flow stops until a client connects. But since you can't execute any statement (remember accept is blocking?) how can a client connect? This chicken and egg problem is resolved through threads. See Howard's answer for a code sample.
I don't see any call to accept(), so I wonder what your client connects to...