MSNP9 is a new protocol that was introduced with MSN Messenger 6. More information about it can be found in the following resources. We plan to address it fully eventually, but for now we can only offer some links.

MSNP9 offers new peer-to-peer features, including things like custom emoticons and display pictures. In my personal opinion, the changes are at least as significant as those in MSNP8, but are just adding new "luxury" features rather than changing fundamental parhs of the protocol.

Indirect connections

MSNP9 allows clients to transmit more information about their NAT or proxy settings. This information is gathered from the "ClientPort" and "ClientIP" fields in the initial profile. The initial profile hasn't changed since MSNP8, so clients which only support MSNP8 could use this information (for example, informing the user about the connection). In a session that has been NATed or proxied, the IP address and/or port will be those of the last NAT or proxy server before the MSN Messenger server. Connections sometimes pass through several NAT and proxy servers on their way to the server - if the client is using a proxy server, but the IP address is different to that of the proxy server, then the connection has been NATed or proxied again somewhere downstream. In an HTTP-proxied connection, ClientPort will always be 0. The official client compares its IP address and source port to that received from the server, and names the type of connection like this:

	Same IP address	Different IP address
Same port	Direct-Connect	IP-Restrict-NAT
Different port	Port-Restrict-NAT	Symmetric-NAT or Unknown-NAT

If the client is somehow unable to determine its connection type, it will label the connection "Unknown-Connect".

Notes by Dave Woods

Dave Woods has a protocol development site, which includes a section on MSNP9. It's available at http://www.chat.solidhouse.com/.

Notes by ZoRoNaX

ZoRoNaX has a site about MSNP9 at http://wisoftware.host.sk/msn6/.

Forum Posts

Several people have posted useful information about MSNP9 on the Discussion Forum. Below is a list of some useful threads in chronological order of their first post.

Re: News on MSNP9 ? is a long thread, mostly discussing formats for p2p data sent between clients.
msnp89 messages discusses the "D" acknowledgement type to MSGs
MSNP9 - File transfer icons? talks about thumbnail images sent along with file transfer requests.
MSNP9: File transfers when both clients are behind NAT (no UPnP) discusses file transfer.
p9 discusses the numbers sent along with status messages by MSN Messenger 6
msnp9 games discusses the P2P games available in Messenger version 6.
QNG ? discusses changes in the MSNP9 QNG reply
SwitchBoard Sessions on MSNP9 ? discusses changes to the switchboard in MSNP9.
Stupid question briefly discusses how few changes there are in MSNP9.
Hypothetic MSNP8 update started (at last!) is (as the name suggests) mostly about MSNP8, but some MSNP9 issues are brought up.
Newbie encryption question talks about how SHA1 works, with particular referesce to its use in MSNP9.
MSN Object talks about the MSNObject structure introduced in MSNP9
Error 715 after PAG discusses changes in mobile paging that are new in either MSNP9 or MSNP10