通过C中的套接字传递具有整数数组的结构

Question

I want to pass structure over a socket in C. I read about it here:

Passing a structure through Sockets in C

but mine problem is that I have inside of a structure array of integers, and I don't know how can I serialize and deserialize it, any advice?

struct packet{
    int id;
    char buffer[512];
    int array[4];
}

Serialize function , it is working but array of integers is missing

size_t encode_pack(packet pack, char *buf){

    size_t pack_len;
    unsigned char *pt = buf;
    *pt++ = (pack.id  >> 24) & 255 ;
    *pt++ = (pack.id  >> 16)& 255;
    *pt++ = (pack.id >> 8) & 255;
    *pt++ = (pack.id & 255);

    strcpy(pt,pack.buffer);
    pt += strlen(pack.buffer)+1;
    pack_len = sizeof(pack.id) + strlen(pack.buffer); 

    return pack_len;

}

Answer 1

You can send like this:

struct packet p;
int socket;
// Todo: Get socket, initialize/populate p
int temp=hton(p.id);
send(socket,&temp,sizeof(temp),0);
send(socket,p.buffer,sizeof(p.buffer),0);
for (size_t i=0;i<4;++i) {
    temp=hton(p.array[i]);
    send(socket,&temp,sizeof(temp),0);
}
// Todo: Check send calls to make sure they succeed

And you can receive like this:

struct packet p;
int socket;
// Todo: Get socket
int temp;
recv(socket,&temp,sizeof(temp),0);
p.id=ntoh(temp);
recv(socket,p.buffer,sizeof(p.buffer),0);
for (size_t i=0;i<4;++i) {
    recv(socket,&temp,sizeof(temp),0);
    p.array[i]=ntoh(temp);
}
// Todo: Check return value of recv calls to make sure data actually received

hton and ntoh refer to a family of functions. You must choose the functions appropriate for your datatype. See here.

Answer 2

Because the sizes of the arrays are known at compile time, you can treat it like the structure in the given example.

Think of char buffer[512]; , for your purposes, as being the same as char buffer0, buffer1, buffer2, ..., buffer511; .

Also, using sizeof(struct packet) will still work - again, because the array sizes are known at compile time, the compiler can take them into account when computing the total structure size.