Bluetooth from Windows to Linux using BlueZ

[Peter Mortier <peter.mortier@xxxxxxxxxx>]

Dear all,
I want to set up a simple bluetooth connection between 2 PC’s, client running Windows and server running Linux.
There is no need for a lot of overhead such as pairing.
I am running the server software on Linux Ubuntu with the following code:

    int serverSocket, clientSocket;
    struct sockaddr_rc serverAddr = {0}, clientAddr={0};

    socklen_t clientAddrSize = sizeof(sockaddr_rc);

    // Create Bluetooth socket
    serverSocket=socket(AF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM);
    if (serverSocket<0)
    {
      perror("socket creation failed: ");
      return false;
    }
    bdaddr_t  bdaddr_any={{0,0,0,0,0,0}};

  // Bind the socket to any local Bluetooth adapter
    serverAddr.rc_family = AF_BLUETOOTH;
    serverAddr.rc_bdaddr = bdaddr_any; // bind to any local Bluetooth adapter
    serverAddr.rc_channel = 25;

    if (bind(serverSocket,(struct sockaddr*)&serverAddr,sizeof(serverAddr))<0)
    {
      perror("Bind failed");
      close(serverSocket);
      exit(EXIT_FAILURE);
    }

    // listen for incoming connections
    if (listen(serverSocket,1) <0)
    {
      perror("Listen failed");
      close(serverSocket);
      exit(EXIT_FAILURE);
    };

    while (true)
    {
      wxPrintf("Waiting for incoming Bluetooth connections...\n");

      // Accept incoming connection
      clientSocket = accept(serverSocket, (struct sockaddr*) &clientAddr,&clientAddrSize);
      if (clientSocket<0)
      {
        perror("accept failed");
        continue;
      }

I am running the client software on Windows 10 with the following code:

    // Create a Bluetooth socket
    m_serverSocket = socket(AF_BTH, SOCK_STREAM, BTHPROTO_RFCOMM);
    SOCKADDR_BTH serverAddr = { 0 };
    if (m_serverSocket == INVALID_SOCKET) {
      return false;
    }

    // Set the address of the remote Bluetooth device to connect to
    serverAddr.addressFamily = AF_BTH;
    serverAddr.btAddr = *reinterpret_cast<BTH_ADDR*>(&m_Server.Address.ullLong); // this is the addres found by function BluetoothFindFirstDevice()
    serverAddr.serviceClassId = RFCOMM_PROTOCOL_UUID;  // I also tried GUID_NULL
    serverAddr.port = 25; // I also tried 0

    // Connect to the remote Bluetooth device
    if (connect(m_serverSocket, reinterpret_cast<SOCKADDR*>(&serverAddr), sizeof(serverAddr)) == SOCKET_ERROR) {
       std::cout << "error: " << WSAGeLastError() << std::endl;
      return false;
    }

The Linux server is listening on port 25 while the Windows client tries to connect to the same port. The client first searches for the server with BluetoothFindFirstDevice and BluetoothFindNextDevice, finds the server bluetoooth address and uses that address to connect. 
The connection on the client then fails with error code 10051 (or sometimes 10060)

On Linux there is no firewall installed, using bluetoothclt I see it is registered and pairable. The bluetooth dongle is plugged into a USB port and is seen as USB2.0-BT. I have tried different ports without success.

I've done some testing with my code. It seems bluetooth is working well with code above in the following circumstances : 
- windows → windows
- linux → linux
- linux → windows
The only thing that doesn't work is: windows → linux

I am told the problem lies in the BlueZ library, but I find this hard to believe. My guesses are I am doing something wrong.

Any help is much appreciated!

Best regards,
Peter