Yahoo! Protocol: Part 10 - Peer To Peer Transfers

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Not all packets are sent through the Yahoo! servers. Sometimes it is best to initiate a direct peer to peer communication between clients. Once a connection has been established, all IM and other traffic travel directly between peers. This type of communication is known as peer to peer (P2P) and is initiated with a Yahoo! service called Yahoo_P2PFileXfer.

The main reason to create a P2P connection is because a large amount of data must be transferred between clients. A direct connection takes extra processing and network traffic burden off the Yahoo! servers. The most common applications that rely upon P2P connections are file transfers, voice conversations, webcams, and certain IMvironments.

 

Figure 26 - P2P File Transfer Request

 

Transferring a file in Yahoo! Messenger is much like downloading a file via HTTP. Yuser1 sends a request to send a file to the recipient Yuser2, as shown in Figure 26. Within this request, the initiatorâs IP address is sent in the form of an http address such as âhttp://forums.xisto.com/no_longer_exists/. Yahoo! messenger then starts a web server from Yserver.exe and listens for incoming requests from Yuser2. When Yuser2 receives the request he has the option to either accept or deny the request as shown in Figure 27. Yuser2 then performs a HTTP GET operation using the supplied http web address from the Yuser1. This sharing scheme does provide a certain level of security for Yuser2 because Yuser2âs IP address is not reveled to Yuser1 unless Yuser2 accepts the file.

 

Figure 27 - File Transfer Request

 

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Edited February 6, 2009 by tansqrx (see edit history)