TCP API¶

The RTK Base provides a TCP socket interface for direct access to GNSS data streams.

Overview¶

Similar to gpstomqtt, the RTK Base opens TCP port 8000 for raw GNSS protocol access.

Connection Details¶

Data Flow¶

From RTK Base to Client¶

All valid packets received from the ZED GNSS module are forwarded:

• NMEA sentences
• UBX protocol packets
• RTCM correction data

From Client to RTK Base¶

Data sent by clients is forwarded to the ZED serial port:

• Configuration commands
• Query requests
• UBX configuration

Use Cases¶

1. Real-time GNSS Monitoring¶

Connect with terminal or custom application:

nc 192.168.4.1 8000

View live NMEA/UBX/RTCM stream.

2. Configuration Tools¶

Send UBX configuration directly:

echo -e '<UBX_BINARY>' | nc 192.168.4.1 8000

3. Third-party Software¶

Compatible with:

• u-center (u-blox software)
• RTKLIB
• Custom GNSS tools

4. Debug and Diagnostics¶

Capture raw data for analysis:

nc 192.168.4.1 8000 > gnss_capture.bin

Protocol Support¶

NMEA 0183¶

Standard GPS sentences:

• $GNGGA - Global positioning system fix data
• $GNGLL - Geographic position
• $GNGSA - GNSS DOP and active satellites
• $GNGSV - GNSS satellites in view
• $GNRMC - Recommended minimum specific GNSS data
• $GNVTG - Course over ground and ground speed
• $GNZDA - Time and date

UBX Protocol¶

u-blox proprietary protocol:

• NAV class - Navigation results
• RXM class - Receiver manager messages
• INF class - Information messages
• ACK class - Acknowledgments
• CFG class - Configuration
• MON class - Monitoring

RTCM¶

RTCM 3.x correction messages:

• 1005 - Stationary RTK reference station ARP
• 1077 - GPS MSM7
• 1087 - GLONASS MSM7
• 1097 - Galileo MSM7
• 1127 - BeiDou MSM7
• 1230 - GLONASS code-phase biases

Connection Example¶

Python Client¶

import socket

# Connect to RTK Base
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(('192.168.4.1', 8000))

# Read data
while True:
    data = sock.recv(1024)
    if data:
        print(data.hex())  # Or parse NMEA/UBX/RTCM

# Send UBX command
ubx_command = bytes([0xB5, 0x62, ...])  # UBX frame
sock.send(ubx_command)

Command Line¶

# View stream
nc 192.168.4.1 8000

# Save to file
cat < /dev/tcp/192.168.4.1/8000 > output.log

# Send and receive
echo '$PUBX,41,1,0007,0003,9600,0*' | nc 192.168.4.1 8000

Configuration¶

Enable/Disable TCP API¶

Via REST API:

# Currently always enabled on port 8000
# Future versions may support configuration

Via Console:

# Check if TCP server is active
netif

# View active connections
dbg task

Performance¶

Bandwidth¶

Typical data rates:

• NMEA only: ~1-2 KB/s
• NMEA + UBX: ~3-5 KB/s
• Full output (with RTCM): ~10-20 KB/s

Latency¶

• Processing delay: <10ms
• Network latency: Depends on connection
• Total: Typically <50ms local network

Troubleshooting¶

Connection Refused¶

Cause: TCP server not running or port blocked

Solution:

• Check RTK Base is operational
• Verify port 8000 is not firewalled
• Restart RTK Base if needed

No Data Received¶

Cause: ZED module not operational

Solution:

• Check ZED status via web interface
• Verify antenna connection
• Review system logs

Garbled Data¶

Cause: Binary protocols not properly decoded

Solution:

• Use protocol-aware tools (u-center)
• Parse binary frames correctly
• Check baudrate settings

Connection Drops¶

Cause: Network issues or timeout

Solution:

• Implement keep-alive in client
• Check WiFi/Ethernet stability
• Reconnect automatically

Security Considerations¶

• TCP API is unauthenticated
• Only available on local network
• No encryption on data stream
• Use MQTT for secure remote access

Comparison with Other Interfaces¶

References¶

• NMEA 0183 Standard
• u-blox UBX Protocol
• RTCM Standard
• REST API
• MQTT API