TCP Connection Plugin

The TCP Connection plugin handles TCP/IP network connections for devices accessible over local networks or the internet.

When to Use TCP

  • Network-enabled cameras and devices
  • WiFi-connected equipment
  • Cloud-based telescope mounts
  • Devices with Ethernet interfaces
  • Remote observatory equipment

Header File 

#include <connectionplugins/connectiontcp.h>

Basic Setup 

class MyDriver : public INDI::DefaultDevice
{
public:
    MyDriver()
    {
        setConnectionMode(CONNECTION_TCP);
        
        tcpConnection = new Connection::TCP(this);
        tcpConnection->setDefaultHost("192.168.1.100");
        tcpConnection->setDefaultPort(9999);
        tcpConnection->registerHandshake([&]() { return Handshake(); });
        
        registerConnection(tcpConnection);
    }

private:
    Connection::TCP *tcpConnection = nullptr;
};

Communication Example 

bool MyDriver::sendCommand(const char *cmd, char *res, int reslen)
{
    int fd = tcpConnection->getPortFD();
    if (fd < 0)
    {
        LOG_ERROR("TCP socket not open");
        return false;
    }

    // Write and read operations are identical to serial
    int nbytes_written = write(fd, cmd, strlen(cmd));
    if (nbytes_written < 0)
    {
        LOGF_ERROR("Write error: %s", strerror(errno));
        return false;
    }

    if (res && reslen > 0)
    {
        int nbytes_read = read(fd, res, reslen - 1);
        if (nbytes_read < 0)
        {
            LOGF_ERROR("Read error: %s", strerror(errno));
            return false;
        }
        res[nbytes_read] = '\0';
    }

    return true;
}

Best Practices

  • Connection Timeouts: Set appropriate timeouts for network operations
  • Keep-Alive: Consider TCP keep-alive for long-running connections
  • Reconnection: Implement automatic reconnection logic
  • Error Handling: Network errors are common, handle gracefully
  • Firewall: Document required ports in driver documentation

Troubleshooting

Connection Refused

  • Verify device IP address and port
  • Check firewall settings
  • Ensure device is powered on and network-accessible

Connection Timeout

  • Ping device to verify network connectivity
  • Check for network congestion
  • Verify correct port number