Take your games online
Unity supports your networking needs with little learning and even less effort. Take your single-player games online, and easily add high-scores, chat and real-time interaction. Unity performs the heavy lifting so you don't have to.
State Synchronization
GameObject position, velocity, animation, and anything else can be synchronized between players using a delta compression algorithm or uncompressed unreliable strategies.
Realtime Networking
Unity makes the complexities of realtime networking easy to negotiate. Turning a single-player game into a networked multiplayer game requires few changes to your existing code and you never have to worry about networking technicalities like NAT punchthrough.
Remote Procedure Calls
Easily call any functions on any other clients, without the need to do marshalling or other network negotiation.
Backend Connectivity
.NET socket libraries can be used for real-time networking, by opening TCP/IP sockets or sending UDP messages. They also make speaking XML and connecting to databases over ODBC or similar easy.
Web Browser Integration
When running in a web browser, the deployed Unity Web Player can communicate seamlessly with the container web page. That way you get javascript communication and full AJAX capabilities.
Web Connectivity
For access to web pages and web services, Unity provides an easy to use WWW interface. Both synchronous and asynchronous modes are supported.
MMO Technology
Unity doesn't currently come with built in functionality to build full scale Massively Multiplayer games, but a number of companies have come to the rescue with solid technology and polished Unity integration. Following are but a few examples of excellent technologies which are available to both companies and individuals (ordered alphabetically).
Electrotank Universe Platform
Electrotank's Universe Platform provides a powerful and feature-rich back-end for MMOs based on Unity.
Electrotank website
Photon Socket Server
Exit Games' Photon server product powers several major Unity games, including Paradise Paintball with over 600,000 monthly active users. Photon is free for up to 50 users and scales from there.
Photon website
Smartfox Server
Smartfox Server powers several Unity games for both web and iPhone, including the children's MMO Jumpstart. Their licensing includes a free learning edition, and they provide freely downloadable Unity bindings to make it easy to get started.
Smartfox website
Smartfox & Unity SDK