data method
Ordinary data packet (peer -> peer).
payload is the message body.
sn is the data serial number.
index is the fragment offset within the transfer.
count is the total number of fragments.
command stays 0 (C=0) to keep the header small.
Returns a DATA packet.
Implementation
DirectPacket data(Uint8List payload, {
required int sn,
int index = 0,
int count = 1,
}) => DirectPacket.create(
ack: 0,
sn: sn,
index: index,
count: count,
command: Command.EMPTY, // 0
payload: payload,
);