X Window System games

In 1986, MIT and DEC released the X Window System, which provided two important capabilities in terms of game development. Firstly, it provided a widely deployed graphics system for workstation computers on the Internet. A number of workstation graphics systems existed, including Bell Labs' BLIT, SGI's IRIS GL, Carnegie Mellon's Andrew Project, DEC's UWS (Ultrix Workstation Software), VWS (Vax Workstation Software), and Sun's NeWS, but X managed over time to secure cross-platform dominance, becoming available for systems from nearly all workstation manufacturers, and coming from MIT, had particular strength in the academic arena. Since Internet games were being written mostly by college students, this was critical.

Secondly, X had the capability of using computers as thin clients, allowing a personal workstation to use a program which was actually being run on a much more powerful server computer exactly as if the user were sitting at the server computer. While remote control programs such as VNC allow similar capabilities, X incorporates it at the operating system level, allowing for much more tightly integrated functionality than these later solutions provide; multiple applications running on different servers can display individual windows. For example, a word processor running on one server could have two or three windows open while a mail reader running on the workstation itself, and a game running on yet another server could each display their own windows, and all applications would be using native graphics calls. This meant that starting in the summer of 1986, a class of games began to be developed which relied on a fast host computer running the game and "throwing" X display windows, using personal workstation computers to remotely display the game and receive user input. Since X can use multiple networking systems, games based on remote X displays are not Internet-only games; they can be played over DECnet and other non-TCP/IP network stacks.

The first of these remote display games was Xtrek. Based on a PLATO system game, Empire, Xtrek is a 2D multiplayer space battle game loosely set in the Star Trek universe. This game could be played across the Internet, probably the first graphical game that could do so, a few months ahead of the X version of Maze War. Importantly, however, the game itself was not aware that it was using a network. In a sense it was a host-based game, because the program only ran on a single computer, and knew about the X Window System, and the window system took care of the networking: essentially one computer displaying on several screens. The X version of Maze War, on the other hand, was peer-to-peer and used the network directly, with a copy of the program running on each computer in the game, instead of only a single copy running on a server. Netrek (originally called Xtrek II) was a fully network-aware client–server rewrite of Xtrek. Other remote X display based games include xtank and XPilot (1991).[4]