github.com/fatedier/frp

FRP provides a straightforward way to expose services behind NAT, and the configuration is reasonably intuitive once you understand the client-server model. The Go SDK allows embedding frp functionality directly into applications, though most usage involves running the prebuilt binaries with TOML/INI configs.

From a security perspective, frp requires significant hardening work. Authentication defaults to a simple token-based system that's easy to misconfigure. TLS is optional rather than enforced by default, meaning you must explicitly configure encryption or risk exposing tunneled traffic. The authentication token is transmitted in plaintext without TLS enabled. Error messages can be verbose and expose internal network topology details if not carefully managed.

Input validation on proxy configurations exists but I've encountered edge cases where malformed subdomain requests weren't properly sanitized. The project has had CVEs related to authentication bypass and path traversal that were patched, but response time varies. You'll need to implement your own rate limiting and connection tracking if you're exposing this to untrusted networks.

FRP works well for basic reverse proxy scenarios but reveals operational gaps when running in production. The configuration is straightforward with TOML/INI files, and the core tunneling functionality is solid. However, resource management becomes problematic under sustained load - connection pooling is minimal, and you'll need external monitoring since built-in observability is limited to basic file logging.

Timeout configuration exists but defaults are aggressive and not well-documented. Reconnection logic works but lacks exponential backoff customization, leading to thundering herd problems when backends recover. Memory usage can spike unpredictably with many concurrent tunnels, and there's no graceful degradation - it's either working or it's not. Breaking changes between minor versions have bitten us twice, particularly around plugin APIs and authentication mechanisms.

For production use, expect to wrap this with your own health checks, metrics exporters (Prometheus integration is basic), and connection lifecycle management. The codebase is actively maintained but documentation focuses on features rather than operational concerns like proper timeout tuning or load characteristics.

FRP excels at what it does: exposing local services behind NAT through a simple client-server architecture. The INI-based configuration is straightforward for basic scenarios, and you can be up and running in minutes. The documentation covers common use cases like HTTP/HTTPS proxying, TCP forwarding, and SSH tunneling with clear examples. Most developers will find the typical workflow intuitive—configure your frps server, point frpc clients to it, and you're done.

However, using FRP as a Go library rather than a standalone binary reveals some friction. The package isn't designed with programmatic usage as a priority; most examples assume you're running the binaries. When embedding FRP in your application, you'll spend time reading source code to understand the internal APIs since library usage documentation is sparse. Error messages are generally clear for configuration issues but can be vague when dealing with network problems or authentication failures.

Community support is decent—GitHub issues get responses, though sometimes with delays. The maintainers are responsive to bugs but feature requests move slowly. Common pitfalls like port conflicts or firewall issues aren't always well-documented, requiring some trial and error.