CODEWITHSUNDEEP
javaandroidc++qttcp
Dan Snow
Dan Snow

Reputation: 127

java and c++ Clien/server

I made a TCP sever with Qt on windows and I want to make my android app discuss with the server. I was able to connect my app with the server now i want to send a packet to the server I found a way but I will have to change almost all the server code source. The solution is to use a outputStream or a DataStream with android, I know exactly what to do with Qt but i don't know and I don't find the equivalence on Java, can somebody can help me please ? thank you :)

the code of the server:

QDataStream in(idClient);

if (tailleMessage == 0)
{
if (idClient->bytesAvailable() < (int) sizeof(quint16))
    return;
in >> tailleMessage;
}
if (idClient->bytesAvailable() < tailleMessage)
return;

in >> type;
tailleMessage = 0;

the code of my windows client:

  QByteArray typeToServer;
    QDataStream typeOut(&typeToServer, QIODevice::WriteOnly);

    QString type = typeDonnees;
    typeOut << (quint16) 0;
    typeOut << type;
    typeOut.device()->seek(0);
    typeOut << (quint16) (typeToServer.size() - sizeof(quint16));

    socket->write(typeToServer);

I want make something like this with my androis apps instead of (if i use this code i will force to change the code of my server and my window client in order to readLine):

        String str = text01.getText().toString();
        int a= str.length();
        PrintWriter out = new PrintWriter(new BufferedWriter(
                new OutputStreamWriter(socket.getOutputStream())),
                true);
        out.println(a);
        out.println(str);

Upvotes: 0

Views: 381

Answers (2)

BevynQ
BevynQ

Reputation: 8259

Is this what you are after?

private void createClient() throws IOException {
    Socket client = new Socket("server",22222);
    String text = "hello"
    // you can specify encoding of text to bytes by default java is UTF-8
    byte[] message = text.getBytes("ASCII"); 
    // encode length as 2 bytes (short integer) using big endian
    byte[] length = new byte[2];
    length[0] = (byte)(message.length >> 8);
    length[1] = (byte)(message.length & 0x0ff);
    // write message length to socket
    client.getOutputStream().write(length);
    // write message to socket
    client.getOutputStream().write(message);
    client.getOutputStream().close();
    client.close();
    System.out.println("client closed");
}

this is the same as above but only does one output write.

private void createSingleWriteClient() throws IOException {
    Socket client = new Socket("localhost",22222);
    String text = "hello";
    // you can specify encoding of text to bytes by default java is UTF-8
    // encode length as 2 bytes (short integer) using big endian
    byte[] bytes = text.getBytes("UTF-16");
    byte[] message = new byte[2+bytes.length];
    message[0] = (byte)(bytes.length >> 8);
    message[1] = (byte)(bytes.length & 0x0ff);
    System.arraycopy(bytes, 0, message, 2, bytes.length);
    // write message to socket
    client.getOutputStream().write(message);
    client.getOutputStream().close();
    client.close();
    System.out.println("client closed");
}

Upvotes: 1

Alexander L. Belikoff
Alexander L. Belikoff

Reputation: 5711

Assuming you have a C++ server and a Java client (being Android app), your safest choice is to stick to a text (potentially compressed/encrypted) protocol that is compatible with both: XML or JSON. Both C++ and Java have support for either.

Upvotes: 2

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