Multiplayer¶
DOS multiplayer games used two main networking approaches: serial connections (modem dial-up or direct null modem cable) for head-to-head play, and IPX for LAN parties. DOSBox Staging emulates both over modern internet connections.
Tip
For per-game setup instructions and troubleshooting, see the Multiplayer & Serial Ports wiki page.
Serial multiplayer¶
Games like Doom, Rise of the Triad, and Terminal Velocity supported modem or null modem play. DOSBox Staging’s serial port emulation handles both.
Modem mode¶
Modem mode emulates a Hayes-compatible dial-up modem. One player listens for
incoming calls; the other dials their IP address (or hostname) using the
game’s built-in dial-up interface — the same ATDT commands real modems
used, just routed over the internet instead of a phone line.
The host listens on a port:
The client dials the host’s address from within the game, e.g.,
ATDT 203.0.113.5:5000.
Some games have restrictive phone number input fields that won’t accept IP
addresses. You can work around this with a phonebook file — map fake
phone numbers to real addresses in phonebook.txt (or whatever filename
you’ve set via phonebookfile):
Now dialling 5551234 in the game connects to your friend’s machine.
Nullmodem mode¶
Nullmodem mode creates a direct serial link between two DOSBox instances, skipping the modem handshake entirely. This is the simplest option when both players can coordinate outside the game.
The host listens on a port:
The client connects to the host:
The connection is established as soon as both sides start DOSBox — no dialling required. The game sees a standard serial connection on COM1.
ENet reliable UDP transport¶
By default, both modem and nullmodem modes use TCP. Adding sock:1 switches
to ENet, a reliable UDP-based transport. For internet play, ENet is
strongly preferred — it has lower latency than TCP and is more resilient on
unreliable connections. Both sides must use the same transport.
IPX multiplayer¶
LAN-party games like Duke Nukem 3D, WarCraft II, and Command & Conquer used the IPX protocol. DOSBox Staging tunnels IPX over modern UDP/IP. One player starts a server, others connect to it:
See the IPX page for configuration details.
Port forwarding and firewalls¶
In both serial and IPX multiplayer, the host needs the chosen port to be
reachable from the internet. If the host is behind a router or NAT, this
typically means setting up port forwarding for that single port (UDP when
using sock:1 or IPX, TCP otherwise).
If neither player can forward a port, a VPN such as ZeroTier or Tailscale is the easiest alternative — both players join the same virtual network and connect using their VPN-assigned addresses, with no port forwarding needed.