Receiving a Struct and Writing to file in socket programming - c++

Question

How to receive a struct over tcp socket and output to a file? I have a struct, which is a packet and I'm trying to send this over socket and receive it on the client side and write to the file. I'm using a void pointer as the buffer to store the file data
So far I have
struct packet {
int id;
void* data;};
I'm able to access the id, the int on the client side but when i write the data out to file. the file seems to be corrupted.
UPDATE:
The Server has a file open and will read from the file and make it into a packet and send the packet to the client.
Client will also have a file open for write, as it receives the packets it will write it out to the file.
Server Side:
current_packet = 0;
While(1)
{
struct packet *current = (packet *)malloc(packet_size+sizeof(int));
current->id = current_packet;
int read = fread(&current->data, 1, packet_size, file);
//end of file
if(read == 0){
break;
}
int byte_write = write(conn, current,read + sizeof(int));
current_packet++;
}
Client Side
current_packet = 0;
While(1)
{
struct packet *current = (packet *)malloc(packet_size+sizeof(int));
int read = read(conn, current, packet_size + sizeof(int));
//end of file
if(read == 0){
break;
}
int byte_write = fwrite(&current->data, 1, read - sizeof(int), file);
fflush(file);
}

Answer 1

struct packet *current = (packet *)malloc(packet_size+sizeof(int));
Supposed packet_size is something like
const size_t packet_size = 2048;
The code cited above might allocate something big enough to contain a packet, but the data pointer isn't initialized, and also not considered correctly in the allocation.
What I would do in your case:
Have a fixed size buffer allocated per packet like this:
struct packet {
const size_t packet_size = 2048;
int id;
std::array<unsigned char,packet_size> data;
};