get socket's local address and foreign address

get_sock_addr.cc

#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <string>

std::string get_local_addr(int sockfd) {
  struct sockaddr_in sin;
  socklen_t len = sizeof(sin);
  int rc = getsockname(sockfd, (struct sockaddr*)&sin, &len);
  if (rc != 0) {
    // error
    return "";
  }
  std::string host(inet_ntoa(sin.sin_addr));
  int port = ntohs(sin.sin_port);
  return host + ':' + std::to_string(port);
}

std::string get_foreign_addr(int sockfd) {
  struct sockaddr_in sin;
  socklen_t len = sizeof(sin);
  int rc = getpeername(sockfd, (struct sockaddr*)&sin, &len);
  if (rc != 0) {
    // error
    return "";
  }
  std::string host(inet_ntoa(sin.sin_addr));
  int port = ntohs(sin.sin_port);
  return host + ':' + std::to_string(port);
}

#include <iostream>

int main(int argc, char** argv) {
  struct sockaddr_in sin;
  sin.sin_family = AF_INET;
  inet_aton(argv[1], &sin.sin_addr);
  sin.sin_port = htons(atoi(argv[2]));
  int sockfd = socket(AF_INET, SOCK_STREAM, 0);
  connect(sockfd, (struct sockaddr*)&sin, sizeof(sin));
  std::cout << "Local Address:   " << get_local_addr(sockfd) << std::endl;
  std::cout << "Foreign Address: " << get_foreign_addr(sockfd) << std::endl;
  return 0;
}