b_ok = bytes("OK\r\n", 'utf-8')

    # Send file over TCP socket in binary chunks of max 4 kBytes.
    def send_file(self):
        chunkSize = 4096
        sizeBytes = os.path.getsize(self.binFilePath)
        totalNofChunks = (sizeBytes + chunkSize - 1) / chunkSize
        with open(self.binFilePath, "rb") as f:
            chunkNr = 1
            while True:
                chunk = f.read(4096)
                if chunk:
                    print("sending part %d of %d (%d bytes)" % (chunkNr, totalNofChunks, len(chunk)))
                    h = bytes(("!%04x" % (len(chunk) + 5)), 'utf-8') + chunk
                    result1 = self.send_command(h)
                    if result1 != b_ok:
                        return result1
                    chunkNr = chunkNr + 1
                else:
                    break;
        return b"OK\r\n"

    def send_command(self, cmd):
        totalSent = 0
        while totalSent < len(cmd):	
            sent = self.socket.send(cmd[totalSent:])				
            if sent == 0:
                raise RuntimeError("Socket connection broken TX")
            totalSent = totalSent + sent
            
        # print("Sent %d bytes, waiting for response..." % totalSent)

        chunks = []
        bytesReceived = 0
        while 1:
            chunk = self.socket.recv(1)
            if chunk == b'':
                print("RX %d bytes" % bytesReceived)
                raise RuntimeError("Socket connection broken RX")
            chunks.append(chunk)
            bytesReceived = bytesReceived + len(chunk)
            if chunk[-1:] == b'\n':
            #if bytesReceived > 3:
                break
        data = b''.join(chunks)
        #print("rx data = '%s'" % data)
        return data