问题
I cannot find documentation anywhere that will tell me what this message means.
it looks like this in Wireshark.
00 00 00 03 14 03 01
I realize it is a 3 byte message, it is an extended message, ie type 20, but I don't know what 03 01 represent.
The scenario is that I send an 'Interested' message to the peer to unchoke my client, the peer then responds with the above message, followed by the 'Unchoke' message.
回答1:
It is a extension message with ID = 3 and 01 is message data.
What ID = 3 means in this case, is defined by the previously extended message handshake (ID = 0) your client has sent.
A educated guess is that the message you see means: upload_only = 1. ('Extension for Partial Seeds' - BEP21)
Addendum:
uTorrent and most other clients implementation of upload_only differs from the 'out of date' specification explained here; alus = Greg Hazel
It's defined as a extension message in the extension handshake were the 1 byte message data means: 0x00 = false or < anything else> = true.
This can be verified by using Wireshark.
来源：https://stackoverflow.com/questions/44110910/bittorrent-extended-message