Invalid conversion from 'const char' to 'uint8_t*' [closed]

Question

I am just a newbie, don't know how to solve this issue

void loop()
{
  UdpSend("Test", "192.168.0.240", 4210);
}

void UdpSend(const char* message, uint8_t * ipaddress, int port){
      Serial.println("Send message: ");
      Udp.beginPacket(ipaddress, port);
      Udp.write(message);
      Udp.endPacket();
}

Arduino IDE can't compile.

The error message: invalid conversion from 'const char' to 'uint8_t* {aka unsigned char*}' [-fpermissive]*

Trying to change with this code:

void UdpSend(uint8_t * message, uint8_t * ipaddress, int port){
      Serial.println("Send message: ");
      Udp.beginPacket(ipaddress, port);
      Udp.write(message);
      Udp.endPacket();
}

Also doesn't work, the error message: invalid conversion from 'const char' to 'uint8_t* {aka unsigned char*}' [-fpermissive]*

Please help...

Answer 1

In ESP32 Arduino package the WiFiUdp.h doesn't pull in all Print class write functions. As consequence the WiFiUdp class doesn't know write(const char *str).

Use Udp.print(message); if message is a zero-terminated char array

or Udp.write(message, size); if message is a byte array

Answer 2

Not sure why you're using uint8_t at all

The Udp.beginPacket function signature is

int WiFiUDP::beginPacket(const char *host, uint16_t port)

No hint of uint8_t there

and .write is either

WiFiUDP::write(uint8_t byte)
WiFiUDP::write(const uint8_t *buffer, size_t size)
WiFiUDP::write(const char *str)
WiFiUDP::write(const char *buffer, size_t size)

So, your other attempt to use write((uint8_t *)) is also wrong

Try this:

void loop()
{
  UdpSend("Test", "192.168.0.240", 4210);
}

void UdpSend(const char* message, const char * ipaddress, int port){
      Serial.println("Send message: ");
      Udp.beginPacket(ipaddress, port);
      Udp.write(message);
      Udp.endPacket();
}