TCP Server is running on an Arduino - Clients are from a PC (using WatsonTCP)

[jimmie11]

Thank you very for making this great library.

I have a TCP server running on an Arduino. The Arduino TCP server will only be connected to Watson TCP clients running on a PC.

Can you help me with the code for the additional header on the Arduino side? I know it is explained in the link below but I do not know how to implement it on the Arduino side.

https://github.com/jchristn/WatsonTcp/blob/master/FRAMING.md#integration-with-non-watsontcp-endpoints

Thank you.

[jchristn]

Hi @jimmie11 thanks for your note. What language are you using on the Arduino? I assume Java. While I can't produce the code for you, here's what I would do.

Receive:

1. Read one byte and append to the end of a buffer
2. If the end of the buffer equals \r\n\r\n you've reached the end of the message header, otherwise, go back to step 1
3. JSON-deserialize the buffer and convert the len property's value to an integer
4. Read len bytes from the socket

After step 4, you now have the entire message.

Send:

1. Create a HashMap (or similar dictionary) and set s to Normal, and, len to the integer value representing the amount of data you wish to send
2. JSON serialize the HashMap to a string and send it to the socket (do not use JSON pretty which has newlines, tabs, etc)
3. Send \r\n\r\n to the socket
4. Send your data

Let me know if this helps.

[jimmie11]

Thank you very much Joel. I really appreciate that you took the time to answer my question.

I am programming my Arduino in C (I do not know Java). What I have done (but it is not working) is place the [WatsonTCP Start] bytes before my byte array (which is 266 bytes long). Then, after my array, I placed [WatsonTCP End] bytes as shown below.

[WatsonTCP Start] [mybyteArray] [WatsonTCP End]

My code is below (Server side). I would like to send this array to a WatsonTCP client and would appreciate if you can tell me why it is not working as the client is not receiving the array?

Thanks in advance.

//---------------------------------------------------------------------------

#define MAX_TCP_LENGTH 285

  int msgS = 15;

  //Watson Start
  output[0] = 108;
  output[1] = 101;
  output[2] = 110;
  output[3] = 58;
  //------------------------
  output[4] = 01;
  output[5] = 10;
  //------------------------
  output[6] = 44;
  output[7] = 115;
  output[8] = 58;
  output[9] = 78;
  output[10] = 111;
  output[11] = 114;
  output[12] = 109;
  output[13] = 97;
  output[14] = 108;
//---------------------------------------------------------------------------
myArray(output[0 + msgS]    to  output[265 + msgS])
//---------------------------------------------------------------------------
//Watson End
  output[266 + msgS] = 13;
  output[267 + msgS] = 10;
  output[268 + msgS] = 13;
  output[269 + msgS] = 10;

[jchristn]

Hi @jimmie11 nothing will come after your byte array. All of the Watson header information (including \r\n\r\n) is before your byte array.

For instance:

{"s":"Normal","len":13}\r\n\r\nHello, world!

Would be a byte array containing:

{"s":"Normal","len":13}
7b 22 73 22 3a 22 4e 6f 72 6d 61 6c 22 2c 22 6c 65 6e 22 3a 31 33 7d

then

\r\n\r\n
13 10 13 10

then

Hello, world!
48 65 6c 6c 6f 2c 20 77 6f 72 6c 64 21

So in total, you would send:

{"s":"Normal","len":13}\r\n\r\nHello, world!
7b 22 73 22 3a 22 4e 6f 72 6d 61 6c 22 2c 22 6c 65 6e 22 3a 31 33 7d 13 10 13 10 48 65 6c 6c 6f 2c 20 77 6f 72 6c 64 21

Let me know if this helps. Cheers, Joel

[jimmie11]

T H A N K Y O U !

I appreciate it. It works now after following your very clear directions.

[jimmie11]

Thanks again. Here is how the array should look like:

//Watson Start
output[0] = 123;
output[1] = 34;
output[2] = 115;
output[3] = 34;
output[4] = 58;
output[5] = 34;
output[6] = 78;
output[7] = 111;
output[8] = 114;
output[9] = 109;
output[10] = 97;
output[11] = 108;
output[12] = 34;
output[13] = 44;
output[14] = 34;
output[15] = 108;
output[16] = 101;
output[17] = 110;
output[18] = 34;
output[19] = 58;
output[20] = 50; //2 (message is 266 bytes)
output[21] = 54 ; //6
output[22] = 54 ; //6
output[23] = 125;
output[24] = 13;
output[25] = 10;
output[26] = 13;
output[27] = 10;

[jchristn]

Glad it worked!!!