feat: Implement systemd socket activation

Author: NyCodeGHG

components/index.ts

@@ -79,10 +79,18 @@ import { cheapLoadUserData, setupFileStructure } from "./databaseHandler"
 import { getFlag, saveFlags } from "./flags"
 import { initializePeacockMenu } from "./menus/settings"
 import { ConfigRouteParams } from "./types/gameSchemas"
+import { getSocketActivationFileDescriptors } from "./socketActivation"
 
 const host = process.env.HOST || "0.0.0.0"
 const port = process.env.PORT || 80
 
+const listenFds = getSocketActivationFileDescriptors()
+let listenFd: number | null = null
+
+if (listenFds !== null && listenFds.length > 0) {
+    listenFd = listenFds[0]
+}
+
 function uncaught(error: Error): void {
     if (
         (error.message || "").includes("EADDRINUSE") ||
@@ -577,9 +585,19 @@ export async function startServer(options: {
 
         const httpServer = http.createServer(app)
 
-        log(LogLevel.INFO, `Listening on ${host}:${port}...`)
-        // @ts-expect-error Non-matching method sig
-        httpServer.listen(port, host)
+        if (listenFd !== null) {
+            log(LogLevel.INFO, `Listening on systemd://${listenFd}...`)
+            httpServer.listen({
+                fd: listenFd,
+            })
+        } else {
+            log(LogLevel.INFO, `Listening on ${host}:${port}...`)
+            httpServer.listen({
+                host,
+                port,
+            })
+        }
+
         log(LogLevel.INFO, "Server started.")
 
         if (getFlag("discordRp") === true) {

components/socketActivation.ts

@@ -0,0 +1,40 @@
+/*
+ *     The Peacock Project - a HITMAN server replacement.
+ *     Copyright (C) 2021-2026 The Peacock Project Team
+ *
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU Affero General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ *
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU Affero General Public License for more details.
+ *
+ *     You should have received a copy of the GNU Affero General Public License
+ *     along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+// Partially based on https://github.com/derhuerst/node-systemd/blob/master/lib/systemd.js
+
+const SD_LISTEN_FDS_START = 3
+
+export function getSocketActivationFileDescriptors(): number[] | null {
+    if (process.env.LISTEN_PID === undefined) {
+        return null
+    }
+
+    const pid = parseInt(process.env.LISTEN_PID)
+
+    if (pid !== process.pid) {
+        return null
+    }
+
+    if (process.env.LISTEN_FDS === undefined) {
+        return null
+    }
+
+    const fdCount = parseInt(process.env.LISTEN_FDS)
+    return new Array(fdCount).fill(null).map((_, i) => SD_LISTEN_FDS_START + i)
+}