ntrip-client

Lightweight Java NTRIP client for receiving GNSS RTK correction data. Zero runtime dependencies. Java 11+.

Install

Maven

<dependency>
    <groupId>io.github.christian-sidak</groupId>
    <artifactId>ntrip-client</artifactId>
    <version>0.1.0</version>
</dependency>

Gradle

implementation 'io.github.christian-sidak:ntrip-client:0.1.0'

Usage

List available mountpoints

import io.github.christian-sidak.ntrip.client.NtripClient;
import io.github.christian-sidak.ntrip.sourcetable.Sourcetable;

NtripClient client = new NtripClient.Builder("rtk2go.com", 2101).build();

Sourcetable table = client.getSourcetable();
for (var stream : table.getStreams()) {
    System.out.println(stream.getMountpoint() + " - " + stream.getFormat()
        + " (" + stream.getCountry() + ")");
}

Stream RTCM corrections

import io.github.christian-sidak.ntrip.client.NtripClient;
import io.github.christian-sidak.ntrip.protocol.NtripVersion;

NtripClient client = new NtripClient.Builder("rtk2go.com", 2101)
    .credentials("user@example.com", "none")
    .version(NtripVersion.V1)
    .build();

// Decoded RTCM frames
client.stream("MY_MOUNT", frame -> {
    System.out.println("RTCM type " + frame.getMessageType()
        + ", " + frame.getPayload().length + " bytes");
});

Stream raw bytes

// Raw correction data (forward to a GNSS receiver)
client.streamRaw("MY_MOUNT", chunk -> {
    serialPort.write(chunk);
});

VRS (Virtual Reference Station)

For network RTK mountpoints that require your position:

String gga = "$GPGGA,115739.00,4158.8441,N,09147.4417,W,1,08,0.9,255.7,M,-32.0,M,,*6E";

NtripClient client = new NtripClient.Builder("caster.example.com", 2101)
    .credentials("user", "pass")
    .build();

// Start streaming in a separate thread
new Thread(() -> {
    try {
        client.stream("VRS_MOUNT", gga, frame -> {
            System.out.println(frame);
        });
    } catch (IOException e) {
        e.printStackTrace();
    }
}).start();

// Update position periodically
client.sendGga("$GPGGA,115740.00,4158.8442,N,09147.4418,W,1,08,0.9,255.7,M,-32.0,M,,*6F");

Use the RTCM decoder standalone

import io.github.christian-sidak.ntrip.rtcm.RtcmDecoder;

RtcmDecoder decoder = new RtcmDecoder(inputStream);
decoder.decode(frame -> {
    System.out.println("Message type: " + frame.getMessageType());
});

API

NtripClient

Built with NtripClient.Builder:

Method	Description
Builder(host, port)	Create builder with caster address
.credentials(user, pass)	Set Basic auth credentials
.version(NtripVersion)	Set protocol version (V1 or V2, default V1)
.connectTimeout(ms)	Connection timeout (default 10s)
.readTimeout(ms)	Read timeout (default 30s)

Method	Description
getSourcetable()	Fetch and parse the caster's sourcetable
stream(mountpoint, consumer)	Stream decoded RTCM frames
stream(mountpoint, gga, consumer)	Stream with GGA for VRS
streamRaw(mountpoint, consumer)	Stream raw byte chunks
sendGga(sentence)	Send updated GGA on active connection
close()	Disconnect

RtcmDecoder

Streaming decoder for RTCM 3.x binary frames. Scans for 0xD3 preamble, validates CRC-24Q, extracts message type and payload.

Sourcetable

Parsed sourcetable with getStreams(), getCasters(), getNetworks(), findStream(name), and getRtcm3Streams().

NTRIP Protocol Support

Feature	Status
NTRIP v1 (ICY 200 OK)	Supported
NTRIP v2 (HTTP/1.1 chunked)	Supported
Basic authentication	Supported
RTCM 3.x frame decoding	Supported
CRC-24Q validation	Supported
Sourcetable parsing (STR/CAS/NET)	Supported
VRS (GGA position updates)	Supported

License

MIT