Players get disconnected with a buffer or message overflow, or the server console spits out SZ_GetSpace errors during heavy fights. GoldSrc packs game state and events into fixed-size network buffers each frame. When the engine tries to write more into a buffer than it holds — too many entities in view, too many simultaneous messages, a plugin flooding HUD or chat — it overflows, and depending on which buffer, either a client drops or the server errors. The cure is to reduce what is being crammed into the buffer.
1. Identify which overflow you have
The two you will actually see are:
SZ_GetSpace: overflow on netchan->message
and
Reliable channel overflowed for <player>
The reliable-channel overflow is per client: one player is being sent more reliable data than their channel can carry, and the engine drops them to protect the connection. The generic SZ_GetSpace overflow is the buffer running out of space while the engine or a plugin writes to it. Both come down to volume — the difference is whether it is one player's channel or a shared buffer.
2. Suspect entity and effect density first
The most common non-plugin cause is simply too much happening at once: a corner packed with players, grenades, smoke, decals, and temporary sprites. Each visible entity and effect costs bytes in the update. On a high-slot server a single choke point can push a client's update past the buffer. If overflows cluster around the busiest map areas and biggest fights, this is your cause — and it overlaps with the edict pressure covered in the MAX_EDICTS fix.
3. Find the chatty plugin
A plugin that sends large or frequent messages is the other big cause. Watch for:
- HUD plugins redrawing a big status panel every frame instead of on change.
- Advert or info plugins printing long colored messages to everyone at once.
- Effect plugins firing many temporary-entity messages per kill or per shot.
- Menu or scoreboard plugins rebuilding on every event.
Disable suspects one at a time in plugins.ini, change map, and see whether the overflow stops. A plugin that blasts a per-frame HUD message to 32 players is a classic trigger.
4. Reduce the volume
Once you know the source, cut it down:
- Lower decal churn with a stricter
decalfrequencyso sprays and bullet marks do not pile bytes into every update. - Trim cosmetic effect plugins on high-population servers where the buffer headroom per client is smallest.
- For a plugin you control or can configure, make HUD updates event-driven, not per-frame, and shorten message text.
- Reduce slot count if you are running far more players than the map and plugin set can serialize per frame.
Do not reach for exotic net cvars as a first move — the overflow is caused by content volume, and tuning rates around it just moves the crash. Cut the source.
5. Distinguish a server crash from a client kick
It matters who actually goes down. A Reliable channel overflowed for <player> line usually drops only that one client — the server survives and everyone else plays on — because the engine protects the connection by disconnecting the overloaded channel. A generic SZ_GetSpace overflow on a shared buffer is worse: it can fault the whole server. If you are losing single players intermittently, hunt the per-client cause (a plugin targeting individuals, or one player sitting in the densest spot). If the entire server drops at once, look at a broadcast — a round-end effect, a bomb explosion, an advert fired to all — that wrote too much to a buffer shared by everyone. Reading which message immediately preceded the crash in the console narrows it fast.
Troubleshooting
Reliable channel overflowed for Xrepeatedly — that specific client is being sent too much reliable data; a plugin is spamming them, or they sit in the densest area. Find the plugin or reduce effects.- Overflows only during big fights — entity/effect density, not a plugin. Cut decals and cosmetic effects.
- Everyone drops at the same moment — a single broadcast message or effect fired to all players overflowed a shared buffer. Look at what event just happened (round end, a bomb effect, an advert).
- Started after adding one plugin — that plugin is the source; it sends too much. Reconfigure or replace it.
- Only on 32-slot, fine on 16 — per-frame buffer pressure scales with player count. Reduce slots or the plugin/effect load.
Verification
After cutting the suspected source, recreate the worst case: fill the busiest map area with as many players as you can, throw grenades, spray decals, and trigger the events that used to overflow. A clean console with no SZ_GetSpace or reliable-channel errors through a full heavy round means the volume now fits the buffers. If you isolated a plugin, re-enable it alone to confirm the overflow returns with it and disappears without it — that closes the loop on the cause rather than leaving you guessing.
