go-ntrip

Go NTRIP v2 clients for rovers and correction sources.

The rover client is full-duplex: it reads RTCM corrections while keeping the same caster connection writable for periodic NMEA GGA updates. This is required by VRS and nearest-base casters and is the reason the package uses raw HTTP/1.1 over net.Conn/tls.Conn instead of net/http.Client for streaming sessions.

Features

• NTRIP v2 rover GET streams with full-duplex GGA writes.
• NTRIP v2 source PUT streams with chunked transfer encoding by default.
• HTTPS/TLS with custom tls.Config support.
• Basic authentication.
• Sourcetable fetch and parsing for CAS, NET, and STR records, including parse warnings, round-tripping, stream lookup, network lookup, and nearest-stream selection.
• Managed rover and source stream abstractions with reconnect/backoff.
• Deadline-bound request/header/write operations and read-idle reconnects for autonomous rover links.
• NMEA GGA formatting and checksum validation helpers.
• Standard-library only.

Differentiation

Most existing Go NTRIP packages are useful but incomplete for modern rover integrations:

• github.com/go-gnss/ntrip provides a good sourcetable model and warning-oriented parser. Its rover client uses net/http and exposes only resp.Body, so it cannot send periodic GGA on the same active rover stream.
• github.com/de-bkg/gognss/pkg/ntrip has a higher-level client API, sourcetable helpers, and caster metadata handling, but its public rover stream shape is read-only.
• github.com/bezineb5/ntrip-client explores registry and nearest-station selection on top of go-gnss/ntrip; this package includes nearest-stream helpers directly while keeping the transport full-duplex.
• github.com/facebook/time/ntrip has a clean source/push client API; this package covers both source PUT and rover GET with GGA.

This package is differentiated by treating NTRIP v2 as an HTTP/1.1-shaped protocol over a bidirectional TCP/TLS stream for rover sessions. The low-level Rover remains an io.Reader for RTCM and exposes WriteGGA for upstream NMEA updates. The managed RoverStream adds reconnect/backoff and periodic GGA resend without hiding the raw bytes.

Production Defaults

• Dial timeout: 10 seconds.
• Response header timeout: 10 seconds.
• Write timeout: 5 seconds.
• Rover read-idle timeout: 60 seconds.
• Reconnect backoff: 500 milliseconds to 30 seconds, factor 2.

Managed streams retry transient network and server failures. They stop on invalid local configuration and non-transient status responses such as 401 Unauthorized, so supervisors can surface real operator action items instead of looping forever.

Rover

rover, err := ntrip.DialRover(ctx, ntrip.RoverConfig{
    URL: "https://corshub.peinser.com/*",
    Credentials: ntrip.Credentials{Username: "rover", Password: "secret"},
})
if err != nil {
    return err
}
defer rover.Close()

go func() {
    _ = rover.WriteGGA("$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47")
}()

_, err = io.Copy(rtcmDestination, rover)

Managed Rover Stream

stream := ntrip.NewRoverStream(ntrip.StreamConfig{
    Rover: ntrip.RoverConfig{
        URL: "https://corshub.peinser.com/*",
        Credentials: ntrip.Credentials{Username: "rover", Password: "secret"},
    },
    GGAInterval: 5 * time.Second,
    ReconnectOnEOF: true,
})

if err := stream.SetGGA("$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47"); err != nil {
    return err
}
err := stream.RunToWriter(ctx, rtcmDestination)

Source

source, err := ntrip.DialSource(ctx, ntrip.SourceConfig{
    URL: "https://corshub.peinser.com/BASE-01",
    Credentials: ntrip.Credentials{Username: "base", Password: "secret"},
})
if err != nil {
    return err
}
defer source.Close()

_, err = io.Copy(source, rtcmSource)

Sourcetable

table, err := ntrip.FetchSourcetable(ctx, ntrip.SourcetableConfig{
    URL: "https://corshub.peinser.com",
    Credentials: ntrip.Credentials{Username: "anonymous", Password: "anonymous"},
})
if err != nil {
    return err
}

nearest := table.NearestStreams(50.85034, 4.35171, 50_000)

ParseSourcetable is tolerant: it returns parsed records and stores row-level issues in Sourcetable.Warnings instead of discarding the entire table for one malformed field.

Examples

See examples/ for buildable programs covering:

• Reliable rover streaming with reconnect and periodic GGA dispatching RTCM to UDP.
• Dispatching RTCM to multiple sinks: UDP, file, stdout, or a raw device path.
• Fetching a sourcetable and selecting the nearest fixed mountpoint.
• Publishing source RTCM to a caster with NTRIP v2 PUT.
• Formatting and validating fixed-position GGA sentences.