SIGSWON

Inside SIGSWON / Gameplay networking

How gameplay connects.

The original game runs the match. SIGSWON gives its packets a route through modern networks.

The replacement SierraNW DLL bridges the game’s local UDP traffic to a public relay. Both players contact that relay, so they normally do not need to forward ports on their routers or establish a direct connection to each other.

SIGSWON: original games on modern networks Replacement SierraNW DLLs bridge original game UDP through local sockets and a public relay, with outbound registration and keepalives through each player’s router. SIGSWON / GAMEPLAY NETWORK ARCHITECTURE Original games. Modern network path. The game keeps its original UDP protocol; the replacement DLL carries packets through the relay. PLAYER A · HOME NETWORK SIGSWON · PUBLIC SERVER PLAYER B · HOME NETWORK UDP out UDP out UDP back UDP back Setup Setup Router / NAT Router / NAT Local UDP Local UDP ORIGINAL EXE AOriginal gameOutpost 2 / supported SIGS game ORIGINAL EXE BOriginal gameSame original gameplay protocol LOBBY / TLSMatch setupSign in · rooms · player roster LOCAL BRIDGE AReplacement SierraNWMaps each rival to localhostWraps / unwraps game packetsKeeps running during the game LOCAL BRIDGE BReplacement SierraNWOne local socket per opponentDelivers original packet bytesKeeps running during the game GAMEPLAY / UDP 47820Public UDP relayLearns public IP + UDP portForwards to registered playersGame simulation stays on PCs HELLO → ACK before game handoff 01 The EXE sees local opponents. SierraNW hands it 127.0.0.1 endpoints; no executable patch is needed for this relay path. 02 Both PCs contact the same public relay. Outbound UDP creates router mappings. A HELLO every 10 seconds helps keep them open. Outbound traffic Return traffic No direct A ↔ B connection is required in relay mode.
The SIGSWON v5 relay path. On smaller screens, scroll the diagram sideways to see both players. Download the diagram as PNG ↓

Follow one game packet

  1. Meet in the lobby

    Players sign in, join a room, and start a match. Each replacement DLL registers with the relay and waits for its acknowledgement. It then gives the game a local address for each opponent.

  2. The game sends its usual packet

    The original executable sends a UDP packet to an opponent’s local proxy socket. The DLL adds a relay wrapper containing player IDs, a sequence number, a timestamp, and an integrity tag, then sends it to the public relay.

  3. The relay forwards it

    The relay checks the wrapper and forwards the packet to the recipient’s registered public IP address and UDP port. It transports the data; the original games still run the match.

  4. The other game receives the original bytes

    The recipient’s DLL checks and removes the wrapper, then delivers the original packet to the game’s local UDP socket. Replies take the same route in reverse. The bridge stays active during gameplay, even after the game closes its lobby connection.

Why the router lets replies through

Each PC starts an outbound UDP conversation with the same public server. A typical router creates a temporary mapping for that conversation and allows replies from the relay through it. This can also work behind carrier-grade NAT because neither player needs an unsolicited incoming connection from the other player.

After registration, the DLL sends a HELLO every 10 seconds to help keep the mapping open. Normally, this avoids manual port forwarding and UPnP configuration.

UDP still needs to be allowed. Local firewall permission and a reachable relay are required. This path cannot bypass a network that blocks UDP, and it has no automatic TCP gameplay fallback.

TCP lobby, UDP gameplay

SIGSWON uses TCP/TLS for sign-in, lobby chat, rooms, and match setup. Outpost 2’s actual gameplay uses UDP—even when its multiplayer menu calls the connection “TCP/IP.” The Outpost Universe connection guide documents UDP ports for that mode.

The public relay listens on UDP port 47820 by default. It carries the gameplay traffic separately from the lobby service and database.

What to expect

This relay path does not require a patch to the original game executable. It does require the SIGSWON replacement DLLs and a supported game handoff. Outpost 2 is fully supported and working. Birthright and Lords of Magic are in testing. See the supported games list for current compatibility; this diagram does not establish support for every historical SIGS title.

TLS protects the server’s TCP connections. Gameplay UDP payloads are not encrypted. Public-mode integrity keys are publicly derivable, so their tags do not authenticate a player’s account. Each client checks incoming player IDs against its match roster; the public relay itself does not enforce room membership.

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