# Table of contents:

• Introduction
• Client/Request
• Server/Response
• Examples
  • Client-initiated challenge
  • From server at any time
  • Challenge timeout
• Known changes

# Introduction

CHL is a command introduced with MSNP6.

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

A request to generate a challenge, or a request to solve a challenge. Respond correctly with QRY on a new Transaction ID to continue your connection.

# Client/Request

CHL TrID

# Server/Response

CHL TrID challenge

If this command is sent asynchronously, the Transaction ID will be 0 instead.

Where challenge is usually a 20-character numeric value (but can be any valid string) that is concatenated with the client's Private Key.

NOTE: The last received challenge may be used by multiple QRY responses.

# Examples

# Client-initiated challenge

C: CHL 1
S: CHL 1 12345678901234567890

# From server at any time

S: CHL 0 12345678901234567890

# Challenge timeout

S: CHL 0 12345678901234567890

... some time passes ...

S: OUT

Server disconnects client.

# Known changes

• MSNP11: Changed challenge response (QRY commands) generation algorithm drastically.