const http = require('http');
const UNITY_PORT = process.env.UNITY_MCP_PORT || 3000;
const UNITY_HOST = process.env.UNITY_MCP_HOST || 'localhost';
// Enhanced logging to stderr (so it doesn't interfere with stdout JSON-RPC)
function log(msg) {
console.error(`[Unity MCP Bridge] ${msg}`);
}
// 1. Handle Stdin -> POST to Unity
const readline = require('readline');
const rl = readline.createInterface({
input: process.stdin,
output: process.stdout,
terminal: false
});
rl.on('line', (line) => {
if (!line.trim()) return;
const req = http.request({
hostname: UNITY_HOST,
port: UNITY_PORT,
path: '/message',
method: 'POST',
headers: {
'Content-Type': 'application/json',
'Content-Length': Buffer.byteLength(line)
}
}, (res) => {
let data = '';
res.on('data', chunk => data += chunk);
res.on('end', () => {
if (res.statusCode !== 200) {
log(`Unity returned error ${res.statusCode}: ${data}`);
} else if (data) {
// Forward Unity's response to stdout for the MCP client
console.log(data);
}
});
});
req.on('error', (e) => {
log(`Error posting to Unity: ${e.message}`);
});
req.write(line);
req.end();
});
// 2. Handle SSE from Unity -> Stdout
function connectSSE() {
log(`Connecting to Unity at http://${UNITY_HOST}:${UNITY_PORT}/sse`);
const req = http.request({
hostname: UNITY_HOST,
port: UNITY_PORT,
path: '/sse',
method: 'GET',
headers: {
'Accept': 'text/event-stream'
}
}, (res) => {
if (res.statusCode !== 200) {
log(`Failed to connect to SSE. Status: ${res.statusCode}`);
setTimeout(connectSSE, 5000);
return;
}
log('Connected to Unity MCP Server');
res.on('data', (chunk) => {
const text = chunk.toString();
// SSE format: "data: {json}\n\n"
const lines = text.split('\n');
for (const line of lines) {
if (line.startsWith('data: ')) {
const json = line.substring(6).trim();
if (json) {
// Forward to MCP client via stdout
console.log(json);
}
}
}
});
res.on('end', () => {
log('SSE Connection closed. Reconnecting...');
setTimeout(connectSSE, 1000);
});
});
req.on('error', (e) => {
setTimeout(connectSSE, 5000);
});
req.end();
}
// Start SSE listener
connectSSE();
log('Bridge started. Waiting for MCP client input...');
