Server-Side Behavior and Level Links

This document explains how the GServer serverside setting affects level link handling and client-server interactions.

The serverside Setting

The serverside option in serveroptions.txt controls whether the server automatically handles certain game mechanics:

# Determines whether the server handles certain things like signs and links.
# Don't set to true.
serverside = false

Default Value: true (despite the comment suggesting otherwise)

How It Affects Level Links

When serverside = true (Default)

• Server automatically handles level link collisions

• When a player walks into a level link area, the server warps them

• Server does NOT send PLO_LEVELLINK packets to clients

• Server does NOT send sign data to clients

When serverside = false

• Server sends PLO_LEVELLINK packets to clients when entering levels

• Server sends sign data to clients

• Client must detect when player touches a level link

• Client must send PLI_LEVELWARP to request the warp

• Server respects warptoforall setting for warp permissions

Client Implementation Requirements

When connecting to a server with serverside = false, clients must:

1. Parse PLO_LEVELLINK packets to track level links

   • Sent immediately after PLO_BOARDPACKET when entering a level

   • Contains ALL links as a single newline-terminated string

   • Format: “destlevel x y width height destx desty” (space-separated)

   • Coordinates are in tiles (0-63), not pixels

2. Monitor player position to detect link collisions

3. Send PLI_LEVELWARP when player touches a link

4. Handle special destination values:

   • "playerx" or -1 for X: Keep player’s current X position

   • "playery" or -1 for Y: Keep player’s current Y position

GMAP Considerations

When implementing level links in GMAP mode:

• Edge links between GMAP segments should typically be ignored (automatic GMAP transitions handle these)

• Indoor/dungeon links should be honored (transition to single-level mode)

• Client should track whether current level is part of the GMAP to make this distinction

GServer Source Code References

From PlayerClient.cpp:

// Send links, signs, and mod time.
if (!settings.getBool("serverside", false)) // TODO: NPC server check instead.
{
    pLevel->sendLinksToPlayer(shared_from_this());
    pLevel->sendSignsToPlayer(shared_from_this());
}

From LevelLink.cpp (handling special values):

if (m_destinationX == "-1")
{
    m_constantX = true;
    m_destinationX = "playerx";
}

PyReborn Implementation

PyReborn correctly handles this by:

1. Checking _check_level_links() on every movement

2. Logging when a link is touched

3. Currently waiting for server to handle (needs client-side warp implementation)

Recommendations

• Servers should generally keep serverside = true unless they have custom level link handling

• Clients should support both modes for maximum compatibility

• The comment “Don’t set to true” in serveroptions.txt appears to be incorrect