How to send integer array over udp socket in C?

Question

I have to send an int array over an udp socket. Do I have to convert it as char array or as a sequence of byte? What is the standard solution?

Answer 1

You could just do as follow:

int array[100];
sendto(sockfd, array, sizeof(array), 0, &addr, addrlen);

To recv your array the other side (assuming you always send array of the same size):

int array[100];
recvfrom(sockfd, array, sizeof(array), 0, &addr, &addrlen);

As said in the comments, you have to be carefull about the architecture of the system which send / receive the packet. If you're developping an application for 'standard' computers, you should not have any problem, if you want to be sure:

• Use a fixed-size type (include stdint.h and use int32_t or whatever is necessary for you.
• Check for endianess in your code.

Endianess conversion:

// SENDER   

int32_t array[100] = ...;
int32_t arrayToSend[100];
for (int i = 0; i < 100; ++i) {
    arrayToSend[i] = htonl(array[i]);
}
sendto(sockfd, arrayToSend, sizeof(arrayToSend), 0, &addr, addrlen);

// RECEIVER

int32_t array[100];
int32_t arrayReceived[100];
recvfrom(sockfd, arrayReceived, sizeof(arrayReceived), 0, &addr, &addrlen);
for (int i = 0; i < 100; ++i) {
    array[i] = ntohl(arrayReceived[i]);
}