Extracting IP Address and Port Info from sockaddr_storage - c

Question

I'm currently working on a UDP server that receives a request from a client. The datagram I receive is a byte (char) array 5 elements long, with the final two elements being a port number.
Eventually this server will have to return both the IP address and the port number in a datagram of its own.
I already know how to use inet_ntop and the sockaddr struct I've connected with and received from to print out the ip, but it returns a string that's not in the format I want. For instance:
string1 = inet_ntop(their_addr.ss_family,get_in_addr(
(struct sockaddr *)&their_addr),s, sizeof s);
returns:
127.0.0.1
or:
[1][2][7][.][0][.][0][.][1]
when I need something like:
[127][0][0][1]
Should I be using some sort of character and array manipulation to make my 4-element byte array? Or does a sockaddr have this information in a way that I can leave it in this hex form and return it?

Answer 1

Assuming for IPv4.
After taking the address of your sockaddr_storage or sockaddr structure and casting it to the IPv4 version sockaddr_in, you can then access the individual bytes of the IPv4 address.
struct sockaddr_in *sin = (struct sockaddr_in *)&their_addr;
Then you can take address of the s_addr member which is a 32 bit value (in_addr_t) that holds the 4 bytes of the ip address (in network byte order) and cast it to a pointer to an unsigned char which then lets you access the individual bytes of the value.
unsigned char *ip = (unsigned char *)&sin->sin_addr.s_addr;
printf("%d %d %d %d\n", ip[0], ip[1], ip[2], ip[3]);

Answer 2

You want to probably use getnameinfo() function:
int getnameinfo(const struct sockaddr *sa, socklen_t salen,
char *host, size_t hostlen,
char *serv, size_t servlen, int flags);
E.g.:
struct sockaddr_storage client_addr;
socklen_t client_len = sizeof(struct sockaddr_storage);
/* Accept client request */
int client_socket = accept(server_socket,
(struct sockaddr *)&client_addr, &client_len);
char hoststr[NI_MAXHOST];
char portstr[NI_MAXSERV];
int rc = getnameinfo((struct sockaddr *)&client_addr,
client_len, hoststr, sizeof(hoststr), portstr, sizeof(portstr),
NI_NUMERICHOST | NI_NUMERICSERV);
if (rc == 0)
printf("New connection from %s %s", hoststr, portstr);

Answer 3

Here is a simple immutable class I used for the same purpose you mentioned in your question:
class address_t {
private:
uint16_t m_Port = 0;
std::string m_Ip = "";
public:
address_t(const sockaddr_in & address) {
m_Ip = inet_ntoa(address.sin_addr);
m_Port = ntohs(address.sin_port);
}
uint16_t GetPort() const { return m_Port; }
std::string GetIp() const { return m_Ip; }
std::string ToString() const {
return "IP: " + m_Ip + ", Port: " + std::to_string(m_Port);
}
};