# IP Echo

A small Go web service like `ifconfig.me`: call it from a browser, curl, or another service and it tells you what IP address the server sees.

## What It Teaches

- `net/http` routing with the standard library.
- Reading configuration from environment variables.
- Extracting a client IP safely from `RemoteAddr`.
- Optional proxy header support for deployments behind Nginx, Caddy, or a load balancer.
- Table-focused tests for request parsing and HTTP handlers.

## Run

```powershell
go run ./cmd/ipecho
```

The service listens on `:8080` by default.

```powershell
curl.exe http://localhost:8080/
curl.exe http://localhost:8080/ip
curl.exe http://localhost:8080/json
curl.exe http://localhost:8080/headers
curl.exe http://localhost:8080/user-agent
```

Use another port:

```powershell
$env:ADDR = ":9090"
go run ./cmd/ipecho
```

Trust reverse proxy headers:

```powershell
$env:TRUST_PROXY_HEADERS = "true"
$env:TRUSTED_PROXY_CIDRS = "127.0.0.1/32,::1/128"
go run ./cmd/ipecho
```

Only enable `TRUST_PROXY_HEADERS` when your service is behind a proxy you control. Keep `TRUSTED_PROXY_CIDRS` limited to that proxy; otherwise, anyone can spoof forwarded IP headers.

## Endpoints

| Endpoint          | Response                                                   |
|-------------------|------------------------------------------------------------|
| `GET /`           | Browser dashboard or plain text client IP for CLI requests |
| `GET /ip`         | Plain text client IP                                       |
| `GET /json`       | JSON request metadata                                      |
| `GET /headers`    | Plain text request headers                                 |
| `GET /user-agent` | Plain text user agent                                      |
| `GET /healthz`    | Plain text health check                                    |
| `GET /favicon.ico` | Embedded favicon                                          |

## Test

```powershell
go test ./...
```

## Production

See:

- [Production Guide](docs/production.md)
- [nginx Configuration](docs/nginx.md)

Regenerate icon assets and the Windows executable resource:

```powershell
go generate ./...
```