int message_size = sizeof(message_type) + sizeof(module_type) + sizeof(size_t) + strlen(my_id) + 1;

void* buffer = malloc(message_size);

void* offset = buffer;
offset = concat_value(offset, &MODULE_CONNECTED, sizeof(message_type));

offset = concat_value(offset, &ISE, sizeof(module_type));

concat_string(offset, &my_id, strlen(my_id)+1);

send(socket, buffer, message_size, 0);