Maybe review your other threads on the same subject:
MSB and LSB of the signed value
Signed and Unsigned Variables
Missing basics of signed and unsigned numbers (this was 3 years ago)

Mostly, the data transmission functions like read()/write() or recv()/send() don't give a damn about sign or endianess.

Code:
void SendData(void *data, size_t size)
{
  Transmit();
}
In your other code, you do
Code:
sint32_t a;
uint32_t b;
SendData(&a, sizeof(a));
SendData(&b, sizeof(b));
To SendData(), it's just a simple block of memory of a given size.
It neither needs to know, or cares to know what it actually represents.