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The exposePort() method provides a public HTTPS URL that maps directly to a specific port running inside your sandbox container. Fermion automatically supports ports 3000, 1337, and 1338, allowing you to host web servers, APIs, or other services securely and access them from anywhere. When you start a server inside your sandbox, using commands like node server.js or npm run dev, you can call exposePort(port) to instantly retrieve a URL in the format https://{subdomain}-{port}.run-code.com. This enables you to preview, test, and share live services running within your sandbox without any manual networking setup or tunneling.

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exposePort(port)

Description: Returns the public HTTPS URL for a specific port in the sandbox. The sandbox automatically exposes ports 3000, 1337, and 1338 publicly. Parameters:
ParameterTypeRequiredDescription
port3000 | 1337 | 1338YesPort number (must be one of these three)
Returns: Promise<string> - Public HTTPS URL (format: https://{subdomain}-{port}.run-code.com) Example: 
// Start a server
await sandbox.writeFile({
	path: '/home/damner/server.js',
	content: `
    const http = require('http');
    http.createServer((req, res) => {
      res.writeHead(200, {'Content-Type': 'text/plain'});
      res.end('Hello from Fermion!');
    }).listen(3000, () => {
      console.log('Server running on port 3000');
    });
  `
})

// Run server in background (~/ works in commands, shell expands it)
sandbox.runStreamingCommand({
	cmd: 'node',
	args: ['~/server.js'],
	onStdout: data => console.log(data.trim())
})

// Wait a moment for server to start
await new Promise(r => setTimeout(r, 2000))

// Get public URL
const url = await sandbox.exposePort(3000)
console.log('Access your server at:', url)
// Output: https://abc123xyz-3000.run-code.com

await new Promise(r => setTimeout(r, 30000)) // Wait for 30 seconds