How to read unsigned char from a socket

Question

I have to receive a UDP packet from the socket. In this packet hour, min and sec are sent as UNSIGNED CHAR. When I receive it in a char[] and put in TextBox for displaying it is not displaying the actual data which are sent, but different values.

char buffer[10];
udpSocketRxCDP->readDatagram(buffer, sizeof(buffer));
ui->textEditsec->setText(buffer[2]);   

Please suggest how I can get the actual data.

Answer 1

With the little given information, you might want to explicitly convert unsigned char to char. Consider that some data may get corrupted. However, unless you really need it, you can send the data directly as signed char. We can't know whether it's a good choice or not though.

Answer 2

When you read from a socket, you are reading raw data. If you read it into a char[] buffer and use it as-is then the data is going to be interpreted as char. So either typecast the data to unsigned char when needed:

ui->textEditsec->setText( (unsigned char) buffer[2] );  

Or define a suitable struct and typecast to that instead:

struct mypkt
{
    unsigned char hour;
    unsigned char minute;
    unsigned char second;
    ...
};

ui->textEditsec->setText( ((mypkt*)buffer)->second ); 

Either way, assuming setText() actually expects a char* string as input, then use sprintf() or similar function to format a string:

char str[12];
sprintf(str, "%d", (int) ((mypkt*)buffer)->second);
ui->textEditsec->setText(str);