In which format bitcoin protocol send message?

Question

I'm writing a small p2p network and I don't know if I have to transmit message (between nodes) in clear text or in another format ? How is it for bitcoin protocol ?

Answer 1

in clear text or in another format? How is it for bitcoin protocol?

In binary. With numbers mostly in little-endian byte-order. Over TCP with a conventional target port number.

The details are at https://en.bitcoin.it/wiki/Protocol_documentation

For example:

Message structure

Field Size	Description	Data type	Comments
4	magic	uint32_t	Magic value indicating message origin network, and used to seek to next message when stream state is unknown
12	command	char[12]	ASCII string identifying the packet content, NULL padded (non-NULL padding results in packet rejected)
4	length	uint32_t	Length of payload in number of bytes
4	checksum	uint32_t	First 4 bytes of sha256(sha256(payload))
?	payload	uchar[]	The actual data

Unless message size and volume is important, I would instead use JSON in UTF8 for any protocol I create. You should make your own evaluation.

You might also want to consider the Gossip protocol