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NTRIP Streams

This guide covers how to connect MRTKLIB to NTRIP casters for real-time GNSS correction data, including NTRIP version selection and TLS (encrypted) connections.

NTRIP Path Format

All NTRIP stream paths follow this format:

Text Only
[user[:password]@]host[:port]/mountpoint[?ver=N][&host=HOSTNAME]
Component Description Default
user Username for authentication (none)
password Password (special chars: use %XX encoding) (none)
host Caster hostname or IP (required)
port TCP port 2101 (client), 80 (server)
mountpoint Stream mountpoint name (required)
?ver=N NTRIP version override (1 or 2) auto
&host=HOSTNAME Host header override (for TLS tunnels) (from addr:port)

Special Characters in Passwords

Characters that conflict with the path syntax must be percent-encoded:

Character Encoding
@ %40
: %3A
/ %2F
% %25

MRTKLIB automatically decodes these before authentication.

Example: password p@ss:word becomes p%40ss%3Aword in the path.

NTRIP Versions

MRTKLIB supports both NTRIP v1 and v2.

Feature v1 v2
Protocol ICY / HTTP/1.0 HTTP/1.1
Server request SOURCE command POST with chunked encoding
Transfer encoding Raw stream Chunked (RFC 7230)
Typical port 2101 2101

Version Selection

By default, MRTKLIB uses auto-detection: it sends a v2 request first and falls back to v1 if the caster responds with an ICY (v1) header or rejects the connection.

To force a specific version, append ?ver=N to the mountpoint:

TOML
[streams.input.correction]
type = "ntripcli"
path = "user:passwd@caster.example.com:2101/RTCM3_MOUNT"
TOML
[streams.input.correction]
type = "ntripcli"
path = "user:passwd@caster.example.com:2101/RTCM3_MOUNT?ver=1"
TOML
[streams.input.correction]
type = "ntripcli"
path = "user:passwd@caster.example.com:2101/RTCM3_MOUNT?ver=2"

CLI usage with mrtk relay:

Bash
mrtk relay -in ntrip://user:passwd@caster.example.com:2101/MOUNT?ver=2 \
           -out file://output.rtcm3

TLS Connections (NTRIP 2s)

Some casters require TLS-encrypted connections on port 443 (often called "NTRIP 2s"). Examples include NASA Earthdata CDDIS.

MRTKLIB does not currently include a built-in TLS stack. Use stunnel to create a local TLS tunnel.

Setup with stunnel

1. Install stunnel

Bash
brew install stunnel
Bash
sudo apt install stunnel4

2. Create a configuration file

Create ntrip-tls.conf:

INI
[ntrip-tls]
client = yes
accept = 127.0.0.1:2101
connect = caster.cddis.eosdis.nasa.gov:443

This listens on local port 2101 and forwards traffic over TLS to the remote caster on port 443.

3. Start the tunnel

Bash
stunnel ntrip-tls.conf

4. Connect MRTKLIB through the tunnel

Point MRTKLIB at the local stunnel endpoint. Use &host= to set the correct Host header for the remote caster:

TOML
[streams.input.correction]
type = "ntripcli"
path = "user:p%40ssword@127.0.0.1:2101/MOUNT?ver=2&host=caster.cddis.eosdis.nasa.gov"

Or via CLI:

Bash
mrtk relay -in "ntrip://user:p%40ssword@127.0.0.1:2101/MOUNT?ver=2&host=caster.cddis.eosdis.nasa.gov" \
           -out file://output.rtcm3

Host header is required for most TLS casters

When connecting through stunnel, the NTRIP v2 Host: header defaults to localhost:2101. Many casters use this header for routing and will return 404 if it doesn't match. Always add &host=<real-hostname> when using a TLS tunnel with NTRIP v2.

NASA Earthdata Credentials

NASA Earthdata uses your Earthdata Login credentials. Register at https://urs.earthdata.nasa.gov/. Passwords often contain special characters --- remember to percent-encode @ as %40 and : as %3A in the path.

Alternative: socat (one-liner)

For quick testing without a configuration file:

Bash
socat TCP-LISTEN:2101,fork,reuseaddr \
      OPENSSL:caster.cddis.eosdis.nasa.gov:443

Then connect MRTKLIB to 127.0.0.1:2101 as above.

Troubleshooting

Authentication failure (401)

  • Verify credentials are correct.
  • Check that @ and : in the password are percent-encoded (%40, %3A).
  • Some casters require NTRIP v2 --- try ?ver=2.

Connection refused or timeout

  • Confirm the caster hostname and port are reachable:
    Bash
    nc -zv caster.example.com 2101
  • For TLS casters (port 443), verify the stunnel tunnel is running:
    Bash
    nc -zv 127.0.0.1 2101

Source table received instead of data

  • The mountpoint name is incorrect or does not exist on the caster.
  • Request the source table to list available mountpoints:
    Bash
    mrtk relay -in ntrip://user:passwd@caster.example.com:2101/ \
           -out file://sourcetable.txt

v2 handshake fails, falls back to v1

  • This is normal for v1-only casters. No action needed.
  • Check mrtk run status output: ver_neg = 1 confirms v1 negotiation.
  • To suppress the fallback attempt, use ?ver=1.