LAN search, better error handling for joining servers

main.js

@@ -2,6 +2,8 @@ import { AgentProcess } from './src/process/agent-process.js';
 import settings from './settings.js';
 import yargs from 'yargs';
 import { hideBin } from 'yargs/helpers';
+import { serverInfo, findServers } from './src/utils/mcserver.js';
+import mc from 'minecraft-protocol';
 
 function parseArguments() {
     return yargs(hideBin(process.argv))
@@ -18,12 +20,58 @@ function getProfiles(args) {
     return args.profiles || settings.profiles;
 }
 
-function main() {
+async function getServer() {
+    let server = null;
+    let serverString = "";
+    let serverVersion = "";
+
+    // Search for server
+    if (settings.port == -1)
+    {
+        console.log("No port provided. Searching for LAN server...");
+
+        await findServers(settings.host, true).then((servers) => {
+            if (servers.length > 0)
+                server = servers[0];
+        });
+
+        if (server == null)
+            throw new Error(`No server found on LAN.`);
+    }
+    else
+        server = await serverInfo(settings.host, settings.port);
+
+    // Server not found
+    if (server == null) 
+        throw new Error(`Server not found. (Host: ${settings.host}, Port: ${settings.port}) Check the host and port in settings.js.`);
+
+    serverString = `(Host: ${server.host}, Port: ${server.port}, Version: ${server.version})`;
+
+    if (settings.minecraft_version === "auto")
+        serverVersion = server.version;
+    else
+        serverVersion = settings.minecraft_version;
+    
+    // Server version unsupported / mismatch
+    if (mc.supportedVersions.indexOf(serverVersion) === -1)
+        throw new Error(`A server was found ${serverString}, but version is unsupported. Supported versions are: ${mc.supportedVersions.join(", ")}.`);
+    else if (settings.minecraft_version !== "auto" && server.version !== settings.minecraft_version)
+        throw new Error(`A server was found ${serverString}, but version is incorrect. Expected ${settings.minecraft_version}, but found ${server.version}.`);
+    else
+        console.log(`Server found. ${serverString}`);
+
+    return server;
+}
+
+async function main() {
     const args = parseArguments();
     const profiles = getProfiles(args);
     console.log(profiles);
     const { load_memory, init_message } = settings;
 
+    // Get server
+    const server = await getServer();
+
     for (let i=0; i<profiles.length; i++) {
         const agent = new AgentProcess();
         agent.start(profiles[i], load_memory, init_message, i);

src/utils/mcserver.js

@@ -0,0 +1,84 @@
+import net from 'net';
+import mc from 'minecraft-protocol';
+
+/**
+ * Scans the IP address for Minecraft LAN servers and collects their info.
+ * @param {string} ip - The IP address to scan.
+ * @param {number} port - The port to check.
+ * @param {number} timeout - The connection timeout in ms.
+ * @returns {Promise<Array>} - A Promise that resolves to an array of server info objects.
+ */
+export async function serverInfo(ip, port, timeout = 100) {
+    return new Promise((resolve) => {
+
+        setTimeout(() => {
+            resolve(null); // Resolve as null if no response within timeout
+        }, timeout);
+
+        mc.ping({
+            host: ip,
+            port
+        }, (err, response) => {
+            if (err) return resolve(null);
+
+            const serverInfo = {
+                host: ip,
+                port,
+                name: response.description.text || 'No description provided.',
+                ping: response.latency,
+                version: response.version.name
+            };
+
+            resolve(serverInfo);
+        });
+    });
+}
+
+/**
+ * Scans the IP address for Minecraft LAN servers and collects their info.
+ * @param {string} ip - The IP address to scan.
+ * @param {boolean} earlyExit - Whether to exit early after finding a server.
+ * @param {number} timeout - The connection timeout in ms.
+ * @returns {Promise<Array>} - A Promise that resolves to an array of server info objects.
+ */
+export async function findServers(ip, earlyExit = false, timeout = 100) {
+    const servers = [];
+    const startPort = 49000;
+    const endPort = 65000;
+
+    const checkPort = (port) => {
+        return new Promise((resolve) => {
+            const socket = net.createConnection({ host: ip, port, timeout }, () => {
+                socket.end();
+                resolve(port); // Port is open
+            });
+
+            socket.on('error', () => resolve(null)); // Port is closed
+            socket.on('timeout', () => {
+                socket.destroy();
+                resolve(null);
+            });
+        });
+    };
+
+    // Surpress console output
+    const originalConsoleLog = console.log;
+    console.log = () => { };
+    
+    for (let port = startPort; port <= endPort; port++) {
+        const openPort = await checkPort(port);
+        if (openPort) {
+            const server = await serverInfo(ip, port);
+            if (server) {
+                servers.push(server);
+
+                if (earlyExit) break;
+            }
+        }
+    }
+
+    // Restore console output
+    console.log = originalConsoleLog;
+
+    return servers;
+}