// Endpoint.hpp
namespace wiznet_space {
   class Endpoint {
       friend class UDPSocket;
       ....................
   }
}

// Socket.hpp
namespace wiznet_space {

  class Socket {
  public:
       Socket();
  ..........................
  }
}
..........................
..........................

// main.c
..........................

ESP8266Interface wifi(D1, D0, D2, "WizFiDemoAP","12345678",115200); // tx, rx for
wiznet_space::EthernetInterface eth;

bool InitializeWiznetEthernet()
{
    uint8_t mac_addr[6] = {0x00, 0x08, 0xDC, 0xFF, 0x11, 0x22};
 
    eth.init(mac_addr, "192.168.3.102", "255.255.255.0", "192.168.3.1"); //Use DHCP

    .......................................................................................................................    
}

bool InitializeESP8266()
{   
    wifi.init();

    .......................................................................................................................    
}

int main()
{
    ....................................................................

    // Ethernet : WIZnet hardwired TCP/IP in W7500
    if ( InitializeWiznetEthernet() )
    {
        // Send TCP/IP data via Ethernet
        ProcessDataViaEthernet();
    }    
    
    // WiFi : ESP8266
    if ( InitializeESP8266() )
    {
        // Send TCP/IP data via WiFi
        ProcessDataViaWiFi();
    }

    ....................................................................
}

// ProcessDataViaEthernet.cpp
void ProcessDataViaEthernet()
{
    wiznet_space::TCPSocketConnection eth_sock;
    
    eth_sock.connect("192.168.3.64", 6000);
    char send_data[] = "This is from Ethernet Interface\r\n";
    eth_sock.send_all(send_data, sizeof(send_data)-1);
    eth_sock.close();
}

// ProcessDataViaWiFi.cpp
void ProcessDataViaWiFi()
{
    ::TCPSocketConnection wifi_sock;
    
    wifi_sock.connect("192.168.3.64", 6000);    
    char send_data[] = "This is from WiFi Interface\r\n";
    wifi_sock.send_all(send_data, sizeof(send_data)-1);
    wifi_sock.close();
}