Null modem cables are one of the great forgotten technologies of the pre-networking era — a way to connect two computers directly via their serial ports and transfer data or play multiplayer games without any network hardware whatsoever. Two RS-232 connectors, a cable with the transmit and receive lines crossed (hence “null modem” — eliminating the need for a modem), and you had a direct computer-to-computer link. For gaming in the early 1990s, this was genuinely exciting.
The Setup
Getting two machines to communicate via null modem required configuring the serial ports correctly — baud rate, data bits, stop bits, parity all had to match on both ends. DOS-era games that supported serial link play would have configuration screens for exactly this. The speeds achievable (typically 115,200 baud at most) were modest, but for turn-based games or simple action games it was perfectly adequate. The experience of playing a game against another human on a physically connected machine felt futuristic in a way that’s hard to convey now.
The Legacy
Null modem gaming was a stepping stone between the single-player era and true networked multiplayer — a bridge technology that gave people their first taste of playing against another human over a wire. The principles of the serial connection (handshaking, flow control, baud rate negotiation) remain relevant in embedded systems and hardware hacking today. What felt like a childhood gaming setup was actually a grounding in serial communication fundamentals.
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