Sending Data as Bytes formatted in Hex over TCP

@abocanegra wrote:

So I am trying to get the dataset I am sending as small as possible.
The format is Micrcontroller Pixel R G B
I am able to send it using a string and sendRaw.

However, I am attempting to truncate that so that it sends the hex values as bytes using sendRawBytes.
I don't want any delimiters, but I need a known segment size. I have it working to a degree, but instead of each hex value being a byte each is 2 bytes. For instance, FF isn't reading as 1 byte, but a byte for F and another for F. This doesn't help when I am trying to get the data stream as small as possible. There are over 30000 data sets I need to send and speed is a priority. I am planning a UDP version, but I want the TCP to work as well.

I have tried several things, but currently I am using

 sprintf(tcpData,"%02x%04x%02x%02x%02x",
                            i,//Microcontroller (0-33)
                            j,//Pixel (0-909)
                            structure[i][j][2], //red
                            structure[i][j][3], //green
                            structure[i][j][4] //blue
                            );
                    txMessage += tcpData;

When I send the data I use

 if(!TCPClient.isConnected()){
     TCPClient.setup("localhost",10000);
     TCPClient.sendRawBytes(message.c_str(),message.length());
     TCPClient.close();
     ofSleepMillis(4);
  }

The length of the message is like 360360, and the python code parsing it needs to read it as though it is 12 bytes. I want it to be half that and each segment only being 6 bytes. For example, MC(33)Pixel(909)r(255)g(255)b(255) should read as 21038dffffff and be 6 bytes (0x21 0x038d 0xff 0xff 0xff).

I am still fairly new to this sort of thing so I appreciate any help. I have tried sscanf as well, but the output, while accurately showing the number of bytes was pointing to the wrong data:

sscanf(tcpData,"%02x%04x%02x%02x%02x",
                            &i,//Microcontroller (1-33)
                            &j,//Pixel (0-909)
                            &structure[i][j][2], //red
                            &structure[i][j][3], //green
                            &structure[i][j][4] //blue
                            );

with sscanf formatting data Python prints out bytearray(b'\x80\xf280\xfc\x7f\x80') for the first 6 bytes, when it should be bytearray(b'\x01\x0000\x04\x0e\x16'). The total bytes shown is correct though, at 176910.

When I send it to python formatted with sprintf python prints out bytearray(b'010000040e16') for the first 12 bytes for a total message of 353820.

*I have been able to send it as csv values as a string and that works, but is over twice the data I want to be sending. Python is splitting the data and sending it to its appropriate raspberry pi, and as the pi only has 100mb ethernet coupled with the amount of data, I can only get 15fps consistently. If I can cut the dataset in half I am likely able to increase the fps.

If more code is needed to get me in the right direction that is no problem.

Thanks for any help.

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