BitTorrent protocol analysis Six __bittorrent protocol

u l int process_handshake_msg (Peer *peer,unsigned char *buff,int len)

Function: Handles a received handshake message.

Parameters: Receive this handshake message from peer; Buff point to handshake message; Len is the length of buff. The Code for the function implementation is as follows:

int process_handshake_msg (Peer *peer,unsigned char *buff,int len)

{

if (Peer==null | | buff==null) return-1;

if (memcmp (info_hash,buff+28,20)!= 0) {//Close the connection if Info_hash inconsistent

Peer->state = CLOSING;

Discard data from the send buffer

Discard_send_buffer (peer);

Clear_btcache_before_peer_close (peer);

Close (Peer->socket);

return-1;

}

Save the peer_id of the peer

memcpy (peer->id,buff+48,20);

(Peer->id) [20] = ' n ';

If you are currently in a initial state, send a handshake message to peer

if (peer->state = = INITIAL) {

Create_handshake_msg (Info_hash,peer_id,peer);

Peer->state = handshaked;

}

If the handshake message has been sent, the state is converted to a handshake state

if (peer->state = = halfshaked) peer->state = handshaked;

Record when the peer message was recently received

If no messages from the peer are received within a certain period of time (for example, two minutes), close the connection

Peer->start_timestamp = time (NULL);

return 0;

}

u l int process_keep_alive_msg (Peer *peer,unsigned char *buff,int len)

Function: Process the keepv_alive message from peer that you just received. The Code for the function implementation is as follows:

int process_keep_alive_msg (Peer *peer,unsigned char *buff,int len)

{

if (Peer==null | | buff==null) return-1;

Record when the peer message was recently received

If no messages from the peer are received within a certain period of time (such as 2min), close the connection

Peer->start_timestamp = time (NULL);

return 0;

}

u l int process_choke_msg (Peer *peer,unsigned char *buff,int len)

Function: Process the received choke message. The Code for the function implementation is as follows:

int process_choke_msg (Peer *peer,unsigned char *buff,int len)

{

if (Peer==null | | buff==null) return-1;

If you are in a unchoke state, the value of some variables in peer is updated after you receive the message

if (peer->state!=closing && peer->peer_choking==0) {

peer->peer_choking = 1;

Peer->last_down_timestamp = 0; Zero time to receive data from the peer recently

Peer->down_count = 0; Zero the number of bytes recently downloaded from the peer

peer->down_rate = 0; To peer the most recent download of data from this

}