Question

I have a C structures in two different machines – server and clients. For example:

struct account {
   int account_number;
   char *first_name;
   char *last_name;
   float balance;
};

My question is what are the possible ways to replicate the data between the machines? Maybe I can try to convert the data in XML and copy it? Or I can use arrays?

Answer 1

The simplest, most lightweight solution – if you have a connection open between the two machines in the form of a FILE* – may be to transmit with fprintf on one end, and decode with fscanf on the other.

protocol.h:

typedef struct _packet packet_t;

struct _packet {
  int account_number;
  char *first_name;
  char *last_name;
  float balance;
};

static const char packet_fmt[]=" acct: %d fname: %s sname: %s balance: %f";

sender:

  ...
  printf(packet_fmt, acct, "Greg", "Benison", bal);
  ...

listener:

...
int n_read = fscanf(fin, packet_fmt, &acct, fname, sname, &balance);

if (n_read == 4)
  printf("Received balance update for %s %s: %f\n", fname, sname, balance);
...

That may suffice for your four-field struct, but if you anticipate its structure changing or growing significantly it may make sense to pursue XML, JSON, or some other more formal encoding.