Java envoi de paquets de prise de contact au serveur minecraft

En regardant cette page http://wiki.vg/Protocol il semble que vous n'écriviez pas assez de données ni dans le bon ordre. Vous devez également utiliser varint qui est un type spécial de représentation de données d'un entier.

Liens pertinents vers ce numéro:

• Protocole de prise de contact
• format de Paquet
• Explication et exemple de Ping du serveur (ce qui implique une poignée de main)

C->S : Handshake State=1
C->S : Request
S->C : Response
C->S : Ping
S->C : Pong

C est le client et S est serveur

En utilisant le wiki et les exemples de code fournis, j'ai modifié votre code pour suivre toute la demande d'état.

public static void main(String [] args) throws IOException {
    String address = "162.244.165.111";
    int port = 48040;

    InetSocketAddress host = new InetSocketAddress(address, port);
    Socket socket = new Socket();
    System.out.println("Connecting...");
    socket.connect(host, 3000);
    System.out.println("Done!");
    System.out.println("Making streams...");
    DataOutputStream output = new DataOutputStream(socket.getOutputStream());
    DataInputStream input = new DataInputStream(socket.getInputStream());

    System.out.println("Done!");
    System.out.println("Attempting handshake... "+host.getAddress().toString());


    byte [] handshakeMessage = createHandshakeMessage(address, port);

    // C->S : Handshake State=1
    // send packet length and packet
    writeVarInt(output, handshakeMessage.length);
    output.write(handshakeMessage);

    // C->S : Request
    output.writeByte(0x01); //size is only 1
    output.writeByte(0x00); //packet id for ping


    // S->C : Response
    int size = readVarInt(input);
    int packetId = readVarInt(input);

    if (packetId == -1) {
        throw new IOException("Premature end of stream.");
    }

    if (packetId != 0x00) { //we want a status response
        throw new IOException("Invalid packetID");
    }
    int length = readVarInt(input); //length of json string

    if (length == -1) {
        throw new IOException("Premature end of stream.");
    }

    if (length == 0) {
        throw new IOException("Invalid string length.");
    }

    byte[] in = new byte[length];
    input.readFully(in);  //read json string
    String json = new String(in);


    // C->S : Ping
    long now = System.currentTimeMillis();
    output.writeByte(0x09); //size of packet
    output.writeByte(0x01); //0x01 for ping
    output.writeLong(now); //time!?

    // S->C : Pong
    readVarInt(input);
    packetId = readVarInt(input);
    if (packetId == -1) {
        throw new IOException("Premature end of stream.");
    }

    if (packetId != 0x01) {
        throw new IOException("Invalid packetID");
    }
    long pingtime = input.readLong(); //read response


    // print out server info
    System.out.println(json);

    System.out.println("Done!");
}

public static byte [] createHandshakeMessage(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, 1); //state (1 for handshake)

    return buffer.toByteArray();
}

public static void writeString(DataOutputStream out, String string, Charset charset) throws IOException {
    byte [] bytes = string.getBytes(charset);
    writeVarInt(out, bytes.length);
    out.write(bytes);
}

public static 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 int readVarInt(DataInputStream in) throws IOException {
    int i = 0;
    int j = 0;
    while (true) {
        int k = in.readByte();
        i |= (k & 0x7F) << j++ * 7;
        if (j > 5) throw new RuntimeException("VarInt too big");
        if ((k & 0x80) != 128) break;
    }
    return i;
}