iptogeo/src/protocol.h

#include <stdint.h>

#define REQ_MAGIC 0x179E08EF

typedef struct {
    uint32_t magic;
#define REQ_VERSION 1
    uint8_t version;
#define REQ_REQ  1
#define REQ_RESP 0
    uint8_t req;
#define REQ_IPV4  4
#define REQ_IPV6 16
    uint8_t err;
    uint8_t ip_type; // 4 or 6
    uint32_t flags;
    uint8_t ip[16]; // ipv4 or ipv6
    uint8_t country_code[4];
} request_t;

enum {
    REQ_ERR_NO_ERR = 0,
    REQ_ERR_BAD_MAGIC,
    REQ_ERR_BAD_VERSION,
    REQ_ERR_BAD_REQ_FIELD,
    REQ_ERR_BAD_IP_VERSION,
    REQ_ERR_UNSUPPORTED_IP_VERSION, // 5
    REQ_IP_NOT_FOUND, // Not really an error
};