Send UDP Package to Python Server

Development Programming & Scripting Multiplayer & Networking
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1

Hi there, I’m following this tutorial to set up a UDP sender but I can only get false result of following variable.

bool connected = Socket->Connect(*addr);

I’m not acquainted with those UDP and network things so not sure why this keeps happening. Anyone may suggest on this?

2

Hello PhoenixThrough,

The tutorial you posted focuses on TCP sockets. UDP and TCP communication is fundamentally different in a few key aspects. One of these major differences is that UDP communication is actually connection-less.

In TCP, the flow looks something like this:

  1. Server is started, and begins “listening” on a given address / port.
  2. A client with knowledge of the address requests a connection to the server.
  3. The server “hears” this request.
  4. The connection is established, and a new socket is created specifically for the server and client to communicate with (note, this connection is actually done via a separate port which is determined at runtime, and which is unique for each client connection).

For UDP, the flow looks more like this:

  1. A UDP “server” is started. This is effectively just a standard client that listens to a specific address / port.
  2. A client with knowledge of the address sends data explicitly tot eh address / port.
  3. The server receives this data (as well as the address / port of where the data was sent from).

    // Initialize the socket.
    
    ///////// Sending Data /////////
    
    uint8* DataToSend;
    int32 NumberOfBytesToSend;
    int32 NumberOfBytesActuallySent;
    int32 TotalNumberOfBytesSent;
    bool SuccessfullySent = true;
    
    // Populate data
    
    // We may not be able to send all the data in a single packet. This typically only happens with very large amounts of data.
    
    while (TotalNumberOfBytesSent < NumberOfBytesToSend)
    {
        // DataToSend+ TotalNumberOfBytesSent = The new head location of the data to send.
        // NumberOfBytesToSend - TotalNumberOfBytesSent: The remaining number of bytes.
        // NumberOfBytesActuallySent: The number of bytes sent this time (return).
        SuccessfullySent = socket->SendTo( DataToSend+ TotalNumberOfBytesSent, NumberOfBytesToSend - TotalNumberOfBytesSent, NumberOfBytesActuallySent );
    
        TotalNumberOfBytesSent += NumberOfBytesActuallySent
    }
    
    // Check to ensure all data was sent.
    
    ///////// Receiving Data /////////
    
    uint8* ReceivedData;
    int32 TotalBufferSize;
    int32 NumberOfBytesReceived;
    bool ReceivedSuccessfully = true;
    ESocketReceiveFlags Flags = ESocketReceiveFlags::None;
    
    ReceivedSuccessfully = socket->RecvFrom( ReceivedData, TotalBufferSize, NumberOfBytesReceived, Flags);
    
    // Ensure the read was successful.
    // Validate the data against your own application protocol / format.

Thanks,
Jon N.

1 Like
3

These types of flows should be valid, regardless what language the server / client are written in, so you should have no problem using Python.