CODEWITHSUNDEEP
csocketsip
David
David

Reputation: 221

Getting the source address of an incoming socket connection

I have a server with a incoming socket from a client. I need the get the IP address of the remote client. Tried searching google for in_addr but it's a bit troublesome. Any suggestions?

Upvotes: 22

Views: 36009

Answers (3)

Eli Bendersky
Eli Bendersky

Reputation: 273756

You need the getpeername function:

// assume s is a connected socket

socklen_t len;
struct sockaddr_storage addr;
char ipstr[INET6_ADDRSTRLEN];
int port;

len = sizeof addr;
getpeername(s, (struct sockaddr*)&addr, &len);

// deal with both IPv4 and IPv6:
if (addr.ss_family == AF_INET) {
    struct sockaddr_in *s = (struct sockaddr_in *)&addr;
    port = ntohs(s->sin_port);
    inet_ntop(AF_INET, &s->sin_addr, ipstr, sizeof ipstr);
} else { // AF_INET6
    struct sockaddr_in6 *s = (struct sockaddr_in6 *)&addr;
    port = ntohs(s->sin6_port);
    inet_ntop(AF_INET6, &s->sin6_addr, ipstr, sizeof ipstr);
}

printf("Peer IP address: %s\n", ipstr);

Upvotes: 39

Craig McQueen
Craig McQueen

Reputation: 43456

Assuming you're using accept() to accept incoming socket connections, getpeername() isn't needed. The address information is available via the 2nd and 3rd parameters of the accept() call.

Here is Eli's answer modified to do it without getpeername():

int client_socket_fd;
socklen_t len;
struct sockaddr_storage addr;
char ipstr[INET6_ADDRSTRLEN];
int port;

len = sizeof addr;
client_socket_fd = accept(server_socket_fd, (struct sockaddr*)&addr, &len);

// deal with both IPv4 and IPv6:
if (addr.ss_family == AF_INET) {
    struct sockaddr_in *s = (struct sockaddr_in *)&addr;
    port = ntohs(s->sin_port);
    inet_ntop(AF_INET, &s->sin_addr, ipstr, sizeof ipstr);
} else { // AF_INET6
    struct sockaddr_in6 *s = (struct sockaddr_in6 *)&addr;
    port = ntohs(s->sin6_port);
    inet_ntop(AF_INET6, &s->sin6_addr, ipstr, sizeof ipstr);
}

printf("Peer IP address: %s\n", ipstr);

Upvotes: 22

caf
caf

Reputation: 239321

Since you say it is an incoming connection from a client, as an alternative to getpeername you can just save the address that was returned by the accept() call, in the second and third parameters.

Upvotes: 2

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