# Table of contents:

# Introduction

CVQ is a command introduced with CVR0.

It is a Dispatch Server command, without either a request or response payload.

Sends the current client information and retrieves the latest avaliable version of the client when there are no other avaliable protocols. For the version of this command that is sent in the main protocols, read CVR.

# Client/Request

CVQ TrID locale system-type system-ver system-arch requesting-library client-version client-identification {user-handle}

Where locale is a 16-bit hexadecimally encoded LCID. 0x0409 is the LCID for English, United States.

Where system-type is a string that defines the operating system you are using, such as winnt.

Where system-ver is the major and minor version of the operating system, such as 5.1.

Where system-arch is the architecture of the processor that is used to run the client, usually i386.

Where requesting-library is the name of the library that requested this CVR, usually MSMSGS or MSNMSGR.

Where client-version is the current client's major, minor and patch version, should be in the format of "{M}M.m.pppp".

Where client-identification is the internal name of the codebase used to create requesting-library, usually MSMSGS, or an empty parameter. Added since MSNP4, but is empty until MSNP8.

Where user-handle is the user's handle. Added since MSNP8.

# Server/Response

CVQ TrID recommended-version recommended-version-2 minimum-allowed-version download-url fallback-url

Where recommended-version is the current version of the client for this system.

Where recommended-version-2 is (usually) the same as recommended-version, Could possibly be a maximum allowed version? (forced downgrade)

Where minimum-allowed-version is the lowest version the server considers "safe" to connect with. If the client's client-version is lower than the server's minimum-allowed-version, the client should automatically disconnect from the server, and request an forced upgrade using the binary provided in download-url.

Where download-url is the file to download and open to update this client to recommended-version.

Where fallback-url is the URL the client opens if it failed to download download-url for any reason.

# Examples

NOTE: This has been line-breaked. Lines beginning with .. followed by a space are continuations of the previous line.

# Old

Only used in the CVR0 implementation of MSNP2 to MSNP7. 

C: CVQ 1 0x0409 win 4.10 i386 MSMSGS 1.0.0863 MSMSGS
S: CVQ 1 5.0.0537 5.0.0537 1.0.0863
.. http://download.microsoft.com/download/msnmessenger/install/5.0/w98nt42kmexp/en-us/setupdl.exe
.. http://messenger.microsoft.com

Client disconnects from server, since it sees that minimum-allowed is above it's client-version.

# New

Since CVR0 in MSNP8. 

C: CVQ 2 0x0409 winnt 5.1 i386 MSNMSGR 6.0.0602 MSMSGS example@hotmail.com
S: CVQ 2 7.0.0813 7.0.0813 6.2.0205
.. http://msgr.dlservice.microsoft.com/download/5/d/9/5d9bb5b2-49c7-4890-94ab-d1d5e44a0e6d/Install_MSN_Messenger.exe
.. http://messenger.msn.com

Client disconnects from server, since it sees that minimum-allowed is above it's client-version.

# Invalid client identification or version

This response may or may not disconnect you. 

C: CVQ 3 0x0409 winnt 5.0 i386 MSNMSGR 99.9.9999 MSMSGS
S: 420 3
C: CVQ 4 0x0409 winnt 5.0 i386 YCOMM 0.1.0023 MSMSGS
S: 420 4

# Invalid language ID 

C: CVQ 5 0x1111 winnt 5.1 MSNMSGR 6.0.0602 MSMSGS example@hotmail.com
S: 710 5

# Invalid CVR 

C: CVQ 6 spaghetti
S: 731 6

Server disconnects client.

# Known changes