This posts raw data bytes to the link stream .  These bytes are raw bytes and have no additional formatting, packetization, or control bytes.

data

The data to be sent is not formatted and is just a group of bytes.  The data can be specified as bytes, strings, hex numbers, binary numbers, and decimal numbers. Here is more information on ways you can specify data.

Example:

raw "Hi" 0xFF 0b10101010

would send the following bytes across the link stream :

72, 105, 255, 170

Related:

Specifying Data, ASCII Codes