Multiple Listing Service Network Protocol Specification

Global Real Estate And Technology Consortium, Inc.

Author and Maintainer: Corey Leong, GR8C Executive Director

Date: March 2011

Version: 1.0

Status

This document specifies a GR8C standards protocol for the Real Estate Industry and Internet community. GR8C requests open discussion and suggestions for improvements. Please refer to the current edition of this document for the standardization state and status of the protocol. Distribution of this document is unlimited.

Copyright Notice

Copyright (C) Global Real Estate And Technology Consortium (2008-12).

Abstract

Sellers list their properties with real estate professionals who enter property information into private databases called Multiple Listing Services (MLS). These MLSs attempt to index listings with serialized numbers that only members of the local real estate association have access to query, insert, and update. In the United States alone, there are over 900 MLSs which unfortunately create redundant, localized MLS numbers causing confusion over specific properties and their respective listing information on the Internet. These duplicated MLS numbers can be anywhere from eight digits or more relaying no meaningful or geographical information to real estate professionals and real estate buyers alike.

This specification introduces a public, standardized numbering system and protocol called Multiple Listing Service Network (MLSN). Similar to the Web, MLSN is an application publicly available on the Internet, but instead of port 80, MLSN is accessible from port 32801. The numbering scheme is comprised of two parts separated by an '@' symbol: (1) a triple-dotted notation of three decimal integers ranging from 1 to 65,535 and (2) a double-dotted notation number composed of a postal code and country code defined by ISO 3166-1. Taking in consideration for expired listings, MLSN numbers have a reusable feature which allows assigning a new, double-dotted notation number to a preexisting triple-dotted number thereby creating a new MLSN number. Together with a standard protocol and unique numbering schema, a Uniform Resource Locator (URL) is available to users for searching for property listings on the Internet.

Contents

  1. Multiple Listing Service Network Protocol Specification
    1. Status
    2. Copyright Notice
    3. Abstract
    4. Introduction
    5. Protocol Specification
    6. Protocol Example
    7. Internationalization (I18N)
    8. Security Considerations
    9. Messaging
    10. The Query
    11. The Scheme
    12. Registrar Assigned Number
    13. @ Symbol
    14. Postal Code
    15. Country Code
    16. Port
    17. Resource
    18. MLSN Resolves Legacy Issues
    19. Benefits of MLSN
    20. Use Cases

Introduction

The MLSN protocol is a request reply messaging service for querying mls property information over the Internet. Similar to the WHOIS protocol, MLSN offers public access to different types of property such as commercial, residential, rentals, land, timeshares, etc.

MLSN is a TCP/UDP-based query protocol for users on the Internet. The protocol messaging between the client and MLSN server is an XML-based format message consumable for machines or human consumption. Security is not handled by the ports, but may be implemented on the client and server application ends respectively.

Protocol Specification

An MLSN server listens on TCP or UDP port 32801 for requests from an MLSN client. The MLSN client makes a text request to the MLSN server, then the MLSN server replies with text content. All requests are terminated with ASCII CR and then ASCII LF. The response might contain more than one line of text, so the presence of ASCII CR or ASCII LF characters does not indicate the end of the response. The MLSN server closes its connection as soon as the output is finished. The closed TCP or UDP connection is the indication to the client that the response has been received.

Protocol Example

A user sends a request to a MLSN server located at mlsn.gr8c.org for property information about "1.1.1@34786.840", the packets on the wire will look like: 

client                                       server at mlsn.gr8c.org

open TCP       ---- (SYN) ------------------------------------>
              <---- (SYN+ACK) ---------------------------------
send query    ----  "1.1.1@34786.840<CR><LF>" ----------------->
get answer    <---- "<xml>Info about 1.1.1@34786.840<CR><LF>" --
              <---- "More info 1.1.1@34786.840</xml><CF><LF>" --
close         <---- (FIN) --------------------------------------
               -----(FIN> -------------------------------------->

Internationalization (I18N)

The MLSN messaging is sent in XML-based format which enables internationalization of characters and strings.

Security Considerations

The MLSN protocol has no provisions for security. MLSN lacks mechanisms for access control and confidentiality. Accordingly, MLSN-based services should only be used for information which is non-sensitive and intended to be accessible to everyone.

Messaging

MLSN Protocol messaging is received in Extensible Markup Language(XML) called Real Estate Metadata Language or Remetal. An MLSN client parses the received message and displays for a human. For example: 

<xml />
  <real:estate>
    <real:residential>
      <real:location/>
      <real:rooms>
        <real:beds/>
        <real:baths/>
      </real:rooms>
      <real:price/>
      <real:size/>
      <real:style/>
      <real:status/>
    </real:residential>
   </real:estate>

The Query

Below is a query example: 

Example: mlsn://1.1.1@34786.840:32801/price

The Scheme

Example: mlsn://1.1.1@34786.840:32801/price

mlsn:// is the scheme for requesting and receiving MLSN messages.

Registrar Assigned Number

Example: mlsn://1.1.1@34786.840:32801/price

@ Symbol

Example: mlsn://1.1.1@34786.840:32801/price

Postal Code

Example: mlsn://1.1.1@34786.840:32801/price

Country Code

Example: mlsn://1.1.1@34786.840:32801/price

Port

Example: mlsn://1.1.1@34786.840:32801/price

Resource

Example: mlsn://1.1.1@34786.840:32801/price

MLSN Resolves Legacy Issues

Benefits of MLSN

Use Cases

MLSN (last edited 2012-04-04 16:24:18 by CoreyLeong)