Question

I am writing an C++ Application which reads several voltages from a device. I receive these measurements in an float[] and I want to send this array via UDP to a MATLAB-Script.

the C++-function sendto needs to get an char[] buffer and I really have no idea how to convert the float[] into a char[] buffer so i can reassemble it easily in MATLAB. Any Ideas?

Another problem i encountered is that line

addr.sin_addr = inet_addr("127.0.0.1");

inet_addr returns an unsigned long, but my compiler tells me that the = operator does not accept an unsigend long datatype on its right side. Any Iideas about this?

Answer 1

You can always treat any object variable as a sequence of bytes. For this very purpose, it is explicitly allowed (and does not violate aliasing or constitute type punning) to reinterpret any object pointer as a pointer to the first element in an array of bytes (i.e. any char type).

Example:

T x;
char const * p = reinterpret_cast<char const *>(&x);

for (std::size_t i = 0; i != sizeof x; ++i) { /* p[i] is the ith byte in x */ }

For your case:

float data[N];
char const * p = reinterpret_cast<char const *>(data);

write(fd, p, sizeof data);