We Keep Coding

Cant send minecraft login packet to server?

Minecraft is a game which also can be played on multiplayer servers. Each server has its own IP and the port is for every server "25565". In generell, for this problem you should be familiar with Minecaft protocol(https://wiki.vg/Protocol#Login_Start). Even if not, I created a hyperlink where you can look for this.
My goal is to create a Minecraft Chatbot, without even open Minecraftlauncher to join any server. I know, there are already a lot of these existing, but I want to create some new commands which the client should send.
In generell, there are two big steps of the joining process when you join a Minecraft server. First, you need a connection sending a handshake (state 1) and "ping-pong". After this, you are connected to the server. This first step works very well, so I think I needn´t to show you. But the second step is the authentification of every client. Herefor I send a handshake (state 2) and then there comes my problem : I always get "java.io.EOFException" as a error message on my second step, sending my username to the Server.
try {
private String host = "hypixel.net";
socket.connect(host, 25565); //I created already a Socket called "socket"
DataOutputStream output = new DataOutputStream(socket.getOutputStream());
DataInputStream input = new DataInputStream(socket.getInputStream()); //socket is for creating streams
byte[] handShakeMessage = createHandshakeMessageLogin(host, 25565);
writeVarInt(output, handShakeMessage.length);
output.write(handShakeMessage);
System.out.println("Send handShakeMessage!");
output.writeByte(0x01); //hopefully the right packet size
output.writeByte(0x00); //packetID
output.writeUTF("ExamplePlayer"); //sending username
}
public void writeVarInt(DataOutputStream out, int paramInt) throws IOException {
while (true) {
if ((paramInt & 0xFFFFFF80) == 0) {
out.writeByte(paramInt);
return;
}
out.writeByte(paramInt & 0x7F | 0x80);
paramInt >>>= 7;
}
}
public static byte [] createHandshakeMessageLogin(String host, int port) throws IOException {
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
DataOutputStream handshake = new DataOutputStream(buffer);
handshake.writeByte(0x00); //packet id for handshake
writeVarInt(handshake, 4); //protocol version
writeString(handshake, host, StandardCharsets.UTF_8);
handshake.writeShort(port); //port
writeVarInt(handshake, 2); //state (2 for login)
return buffer.toByteArray();
}
public void writeString(DataOutputStream out, String string, Charset charset) throws IOException {
byte [] bytes = string.getBytes(charset);
writeVarInt(out, bytes.length);
out.write(bytes);
}
So, as you can see quite a complicated thing I guess. If somebody could answer me, why I´m getting this error message and how to fix it i would be very very happy! Thank you
EDIT: I found a post, which helped me a lot with the connection! Java sending handshake packets to minecraft server

You're writing a packet length prefix of 1, when your packet contains the entire string "ExamplePlayer".
Instead, construct the packet like is done in the createHandshakeMessageLogin function, then send the length as a varint before sending the content of that buffer.

C# Sockets programming, received sockets length isn't correct

I'm doing a chat application between C# clients and a java server.
I need to send a lot of sockets from the server to the client when he connects. I want to send the logs of the day. So I have all logs in a file.txt, and I send them to the new connected client.
For sending them, I have a for loop until all the logs are sent. Here is the loop:
for (String item : Logs) {
client.send("log:" + item);
}
And for the send method:
public void send(String text) {
//'os' is the: Socket.getOutputStream();
//What the server will send to the client
PrintWriter Out = new PrintWriter(os);
// 0 is the offset, not needed
Out.write(text, 0, text.length());
Out.flush();
System.out.println(text.length());
}
So until there, all works well.
Now my problem is: The output stream sends bytes length like '30', '100', '399' who is 'text.length()', and the C# client receive all sockets, but paste 2 or 3 sockets in one.
E.g: if I send with separated sockets (each line is a out.write() and out.flush() because I call the send method for each line)
(Server-side)
log:abcdefghijklmnopqrstuvwxyz123456789101112131415
log:abcdefghijklmnopqrstuvwxyz
log:abcdefghijklmnopqrstuvwxyz123456789101
log:abcdefghijklmnopqrstuvwxyz1234567891011121314151617
log:abcdefghijklmnopqrst
log:abcdefghijklmnopqrstuvwxyzyxwvu
The sockets will be at the end:
(Client-side)
log:abcdefghijklmnopqrstuvwxyz123456789101112131415log:abcdefghijklmnopqrstuvwxyzlog:abcdefghijklmnopqrstuvwxyz123456789101
log:abcdefghijklmnopqrstuvwxyz1234567891011121314151617log:abcdefghijklmnopqrst
log:abcdefghijklmnopqrstuvwxyzyxwvu
And if I check the sockets length in the server side I get like;
20
12
15
17
20
But in the client side;
32
15
37
The sum of multiples sockets put together.. (And sometimes it's 3 sockets put together, and sometimes 2, sometime 4...) I cant understand why...
Here's my Async method for receiving the sockets from the server;
private void callBack(IAsyncResult aResult)
{
String message = "";
try
{
int size = sck.EndReceiveFrom(aResult, ref ip);
if (size > 0)
{
byte[] receive = new byte[size];
receive = (byte[])aResult.AsyncState;
message = Encoding.Default.GetString(receive, 0, size);
Debug.WriteLine(message.Length);
}
byte[] buffer = new byte[1024];
//restart the async task
sck.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref ip, new AsyncCallback(callBack), buffer);
}
catch (Exception) { }
}
Where the int 'size' contains the size of the byte[] received, and here is the problem. How can I get the right sockets I sent from the server?
If I send each socket with delay in the server side (like 15ms), the client can get the sockets one by one. But only if you have a good connection. If your connection do like 200ms of latency, you will get the sockets grouped... So the problem is in the client side (I think...). The server (java) side works correctly, the flush method always send the socket!
UPDATE:
Here are my sockets;
//Global var
EndPoint ip;
public Socket sck;
//How I connect my sockets
private void connect()
{
ip = new IPEndPoint(IPAddress.Parse("127.0.0.1"), mysql.selectPort());
sck = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
try
{
sck.Connect(ip);
}catch(Exception e) {
Debug.WriteLine(e.Message);
}
}

TCP Socket with Python server and Java client

I am trying to exchange some string data between a Python Server (ideally, a Raspberry Pi with some device connected through GPIO) and a Java Client (again, the main target would be an Android app). The following code, anyway, is running on a standard local PC.
This is the code for the server, taken (and slightly modified) from here:
import socketserver
import datetime
class MyTCPHandler(socketserver.StreamRequestHandler):
def handle(self):
now = datetime.datetime.now()
answer = now
self.data = self.rfile.readline().strip()
print("Read!")
if str(self.data) == 'date':
answer = now.date()
elif str(self.data) == 'time':
answer = now.time()
self.wfile.write((str(answer)+"\n").encode('utf-8'))
print("Sent!")
if __name__ == "__main__":
HOST, PORT = "localhost", 9999
with socketserver.TCPServer((HOST, PORT), MyTCPHandler) as server:
print("Server is running on {}, port {}".format(HOST, PORT))
server.serve_forever()
The Java client is the following:
public class SocketTest {
public static void main(String[] args) {
try {
Socket s = new Socket("127.0.0.1", 9999);
PrintWriter out = new PrintWriter(new OutputStreamWriter(s.getOutputStream()));
BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));
out.println("date".getBytes());
String resp = in.readLine();
System.out.println("Received: " + resp);
} catch (IOException ex) {
Logger.getLogger(SocketTest.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
No exception is thrown whatsoever, it just gets stuck waiting for the response on the client side, and I can never see the "Read!" message on the server side.
The "date".getBytes() comes from somewhere on the net where I found that the Python sockets expect bytes (UTF-8), but in Java I'm sending strings directly, so it might be wrong.
Any help will be appreciated!

Turnes out, it was a flushing problem.
Apparently, the buffer is not flushed when the end of line is reached (which is how I was expecting it to behave).
Adding a simple out.flush() solved the problem.

Android socket is connected but doesn't send data

I'm developing an Android client app which talks to server via a plain TCP Socket, let's assume that the server ip 192.168.1.2 and the androdi device ip is 192.168.1.3.
I open the socket, i check if socket is connected (i get true as result) and after that i write a presentation message.
Here is my code
// scoket setup
Sockets = new Socket(addressToConnect, 2015);
s.setSoTimeout(2500);
setTcpNoDelay(true);
// if i'm connected
if (s.isConnected()) {
// wrapping streams
DataInputStream dis = new DataInputStream(s.getInputStream());
DataOutputStream dos = new DataOutputStream(s.getOutputStream());
// sending data
String presentationMessage = "Presentation message content--- TERM";
dos.write(presentationMessage.getBytes("UTF-8");
dos.flush();
// buffers
byte[] readBuffer = new byte[4096];
StringBuffer responseBuffer = new StringBuffer();
// read data until command terminator string is found
boolean readResponse = true;
while (readResponse) {
int dataBufferLength = dis.read(readBuffer);
String chunk = new String(readBuffer, 0, dataBufferLength, "UTF-8"));
responseBuffer.append(chunk);
readResponse = ! chunk.endWith("--- TERM");
}
// Process data here
} else {
// Notify missing connection here
}
// here i close the socket
When i execute this code the execution seems working like a charme until the first read which timesout.
Sniffing the used WIFI network with a third machine i can't see the connection establishment and the written stream even if the code doesn't throw any exception before the read timeout.
I granted the android.permission.INTERNET in manifest.
Are there some other permissions to grant? or what i'm doing wrong?
Executing the same code in a standard Java SE environment everything goes fine.
I'm testing the code on a Nexus 5, Nexus 9 and Samsung S3 and S4 and the project is compatible with API 14+
Edit: Fixed typo in code example

You are reading from dos and writing to dis. You should reverse that.

C++ Client and Java Server

I did a Java Socket server, and a C++ Client.
However, the client connects to the server, without problems.
But when I write something client-server, the server doesn't catch the message.
What I'm doing wrong?
A little bit of the code of the Java Server:
DataInputStream dis=new DataInputStream(usrSocket.getInputStream());
ByteArrayOutputStream out = new ByteArrayOutputStream();
int data;
while((data = dis.read())>=0) {
out.write(data);
}
byte[] bytes = out.toByteArray();
String decrypt = new String(bytes);
if(decrypt.equals("status")){
System.out.println("Status emitted.");
}
System.out.println("Received a message.");
C++ Client writing:
QByteArray qba;
qba.append(text);
sock->write(qba.data());
qDebug() << "Send status";
I need help with that, thank you very much.
(that variable "text" it's a QString)
EDIT
Java server: That's only one part of all the code, the main thread waits for connections (Socket sock = server.accept()) and create a new thread for each user.
The code that I published of the java server, its one part of that threads for the users.
If you need ALL the code, plese tell me.
I will be waiting the answers!
Thank u very much!
Sorry if I answer ya late.

Try this code for Java Server.
ServerSocket ss = new ServerSocket(Port_No);
Socket incomingClient = ss.accept();
InputStream i = incomingClient.getInputStream();
OutputStream o = incomingClient.getOutputStream(); // Use it write to the Client Socket
InputStreamReader isr = new InputStreamReader(i);
BufferedReader br = new BufferedReader(isr);
String str = new String();
while ((str = br.readLine())!=null){
// do what you want with the data received in str.
}

As youre using QTcpSocket, it highly likely that you are running the client in the default asynchronous mode. This means after when you write after calling connectToHost, nothing will be sent as the socket is not connected.
Try using:
socket->connectToHost(hostAddress, hostPort, QIODevice::ReadWrite);
if (socket->waitForConnected()) {
QString text = "test string";
QByteArray array;
array.append(string);
qDebug() << socket->write(array);
} else {
// connect error!
}

Your Java code reads the socket until EOS and then prints something, which by the way is not a decryption operation. Your C++ client writes something and never closes the socket. So the server can never get out of the read loop.

If I read it correctly it is caused by the fact that your client is still running. Read() returns number >= 0 until the client socket is closed.