Question

I have the following struct and I’m trying to send over the network to another application

 struct protocol
  {

     char protocol;
     char field1;
     char field2;
     char field3;
     char field4;
     char field5;
     char field6;
     char field7;
     char field8;
     char msg_id;
     char msg_length;
     char *msg;

  };

The problem I’m having is that I’m not sure how to send this struct over the network as there is a pointer pointing to a string in it, and memcpy the struct to buffer won’t work, is the below the only way to do it?

memcpy (buffer, protocol->protocol, char)
memcpy (buffer, protocol->field1, char)
...
memcpy (buffer, protocol->msg, protocol->length)

then send the buffer

Answer 1

You will need to serialize the structure into a buffer of some sort. Your sequence of copies is correct in concept only; there are a myriad details to resolve:

char buffer[sizeof(struct protocol) + protocol->msg_length]; // Over-allocation

buffer[0] = protocol->protocol;
buffer[1] = protocol->field1;
...
buffer[8] = protocol->field8;
buffer[9] = protocol->msg_id;
buffer[10] = protocol->msg_len;
memcpy(&buffer[11], protocol->msg, protocol->msg_len);

Now you can write the correct length of buffer (11 + protocol->msg_len) to send.

This is particularly simple; there are no endian-ness issues to worry about. Generally, with multi-byte values like short or int or long long, you have to worry about the transmitted byte order.