How to parse Ip and port from http tracker response

问题

I am sending a request to a tracker and get a response

d8:completei2e10:downloadedi1e10:incompletei1e8:intervali1971e12:min intervali985e5:peers18:\235'\027\253\000\000\331e57\374-\033"\022,\270\302e

How to get Peers list or peer IP and port from this response

回答1:

The response from the tracker is bencoded.
Adding some whitespace for clarity:

d
 8:complete
  i2e
 10:downloaded
  i1e
 10:incomplete
  i1e
 8:interval
  i1971e
 12:min interval
  i985e
 5:peers
  18:\235'\027\253\000\000\331e57\374-\033"\022,\270\302
e

The key:peers that has a 18 bytes binary string as value contains peers in the 'compact=1'-form that is specified in: [BEP23 - Tracker Returns Compact Peer Lists] and also in [the wiki]

Every peer is represented by 6 bytes, 4 bytes IPv4 + 2 bytes PORT in bigendian, so the 18 bytes string is for 3 peers.

\235 ' \027 \253 \000 \000=>157 39 23 171 0 0(0*256+0=0)          =>157.39.23.171:0
\331 e 5    7    \374 -   =>227 101 53 55 252 45(252*256+45=64557)=>227.101.53.55:64557 
\033 " \022 ,    \270 \302=>27 34 18 44 184 192(184*256+192=47298)=>27.34.18.44:47298  

(\235 is octal for 157, ' has ASCII value 39 etc.)

来源：https://stackoverflow.com/questions/50094674/how-to-parse-ip-and-port-from-http-tracker-response