#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
void Usage(char *progname);
void PrintOut(int fd, struct sockaddr *addr, size_t addrlen);
int main(int argc, char **argv) {
// Expect the port number as a command line argument.
if (argc != 2) {
Usage(argv[0]);
}
// Populate the "hints" addrinfo structure for getaddrinfo().
// ("man addrinfo")
struct addrinfo hints;
memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_family = AF_INET6; // IPv6 (also handles IPv4 clients)
hints.ai_socktype = SOCK_STREAM; // stream
hints.ai_flags = AI_PASSIVE; // use wildcard "in6addr_any" address
hints.ai_flags |= AI_V4MAPPED; // use v4-mapped v6 if no v6 found
hints.ai_protocol = IPPROTO_TCP; // tcp protocol
hints.ai_canonname = nullptr;
hints.ai_addr = nullptr;
hints.ai_next = nullptr;
// Use argv[1] as the string representation of our portnumber to
// pass in to getaddrinfo(). getaddrinfo() returns a list of
// address structures via the output parameter "result".
struct addrinfo *result;
int res = getaddrinfo(nullptr, argv[1], &hints, &result);
// Did addrinfo() fail?
if (res != 0) {
std::cerr << "getaddrinfo() failed: ";
std::cerr << gai_strerror(res) << std::endl;
return EXIT_FAILURE;
}
// Loop through the returned address structures until we are able
// to create a socket and bind to one. The address structures are
// linked in a list through the "ai_next" field of result.
int listen_fd = -1;
for (struct addrinfo *rp = result; rp != nullptr; rp = rp->ai_next) {
listen_fd = socket(rp->ai_family,
rp->ai_socktype,
rp->ai_protocol);
if (listen_fd == -1) {
// Creating this socket failed. So, loop to the next returned
// result and try again.
std::cerr << "socket() failed: " << strerror(errno) << std::endl;
listen_fd = 0;
continue;
}
// Configure the socket; we're setting a socket "option." In
// particular, we set "SO_REUSEADDR", which tells the TCP stack
// so make the port we bind to available again as soon as we
// exit, rather than waiting for a few tens of seconds to recycle it.
int optval = 1;
setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR,
&optval, sizeof(optval));
// Try binding the socket to the address and port number returned
// by getaddrinfo().
if (bind(listen_fd, rp->ai_addr, rp->ai_addrlen) == 0) {
// Bind worked! Print out the information about what
// we bound to.
PrintOut(listen_fd, rp->ai_addr, rp->ai_addrlen);
break;
}
// The bind failed. Close the socket, then loop back around and
// try the next address/port returned by getaddrinfo().
close(listen_fd);
listen_fd = -1;
}
// Free the structure returned by getaddrinfo().
freeaddrinfo(result);
// Did we succeed in binding to any addresses?
if (listen_fd == -1) {
// No. Quit with failure.
std::cerr << "Couldn't bind to any addresses." << std::endl;
return EXIT_FAILURE;
}
// Success. Tell the OS that we want this to be a listening socket.
if (listen(listen_fd, SOMAXCONN) != 0) {
std::cerr << "Failed to mark socket as listening: ";
std::cerr << strerror(errno) << std::endl;
close(listen_fd);
return EXIT_FAILURE;
}
// Sleep for 20 seconds, then close house.
sleep(20);
close(listen_fd);
return EXIT_SUCCESS;
}
void Usage(char *progname) {
std::cerr << "usage: " << progname << " port" << std::endl;
exit(EXIT_FAILURE);
}
void PrintOut(int fd, struct sockaddr *addr, size_t addrlen) {
std::cout << "Socket [" << fd << "] is bound to:" << std::endl;
if (addr->sa_family == AF_INET) {
// Print out the IPV4 address and port
char astring[INET_ADDRSTRLEN];
struct sockaddr_in *in4 = reinterpret_cast(addr);
inet_ntop(AF_INET, &(in4->sin_addr), astring, INET_ADDRSTRLEN);
std::cout << " IPv4 address " << astring;
std::cout << " and port " << ntohs(in4->sin_port) << std::endl;
} else if (addr->sa_family == AF_INET6) {
// Print out the IPV6 address and port
char astring[INET6_ADDRSTRLEN];
struct sockaddr_in6 *in6 = reinterpret_cast(addr);
inet_ntop(AF_INET6, &(in6->sin6_addr), astring, INET6_ADDRSTRLEN);
std::cout << " IPv6 address " << astring;
std::cout << " and port " << ntohs(in6->sin6_port) << std::endl;
} else {
std::cout << " ???? address and port ????" << std::endl;
}
}
