The IP address is 192.168.23.4. I am able to get the hostname from the ipaddress using the following code snippet:
struct sockaddr_in sa;
char str[INET_ADDRSTRLEN];
inet_pton(AF_INET, "192.168.23.4", &(sa.sin_addr));
struct sockaddr_in saGNI;
char hostname[NI_MAXHOST];
char servInfo[NI_MAXSERV];
u_short port = 27015;
saGNI.sin_family = AF_INET;
saGNI.sin_addr.s_addr = sa.sin_addr.s_addr;
saGNI.sin_port = htons(port);
DWORD dwRetval = getnameinfo((struct sockaddr *) &saGNI,
sizeof(struct sockaddr),
hostname,
NI_MAXHOST, servInfo, NI_MAXSERV, NI_NUMERICSERV);
printf("HostName: %s", hostname);
I am getting an output of the form
ComputerName.domain.com
How do I get the Computername from the hostname?
Eg Input
ComputerName.domain.com
Eg Output
ComputerName
Is there any way to directly get the ComputerName of a system whose IP address is known?
I am looking for the same result as displayed using the Hostname command on the remote system.
Check the manual pages for getnameinfo
http://man7.org/linux/man-pages/man3/getnameinfo.3.html
According to the manual pages, you should set the NI_NOFQDN flags.
NI_NOFQDN
If set, return only the hostname part of the fully qualified
domain name for local hosts.
As suggested by emirc,
the following code is printing Computername:
struct sockaddr_in sa;
char str[INET_ADDRSTRLEN];
inet_pton(AF_INET, "192.168.23.4", &(sa.sin_addr));
struct sockaddr_in saGNI;
char hostname[NI_MAXHOST];
char servInfo[NI_MAXSERV];
u_short port = 27015;
saGNI.sin_family = AF_INET;
saGNI.sin_addr.s_addr = sa.sin_addr.s_addr;
saGNI.sin_port = htons(port);
DWORD dwRetval = getnameinfo((struct sockaddr *) &saGNI,
sizeof(struct sockaddr),
hostname,
NI_MAXHOST, servInfo, NI_MAXSERV, NI_NOFQDN);
printf("HostName: %s", hostname);
Note:
I have changed the flag from
NI_NUMERICSERV
to
NI_NOFQDN
You mean, you want to truncate the string before the first period?
std::string host(hostname);
size_t pos = host.find('.');
if (pos != std::string::npos)
{
host = host.substr(0,pos);
}
strcpy(hostname, host.c_str());
If you are interested in finding the host name of the computer on which the code is running, Boost.Asio could simplify the task:
#include <iostream>
#include <string>
#include <boost/asio.hpp>
int main() {
std::string hostname = boost::asio::ip::host_name();
std::cout << "hostname = " << hostname << std::endl;
}
Note that this needs to be compiled with the -lpthread option.
Related
I have been trying to get a simple SFTP program working with code from this website, but I have not been able to get it to even send out data without it returning error code 10061 (WSAECONNREFUSED). I have tried using Wireshark on the active interface with all firewalls disabled, but it didn't say anything was being sent to the address I gave (ex: 72.196.212.127). However, when I give it a local address like 192.168.1.101, it gives error code 10060 (WSAETIMEDOUT), still not sending out any data on the network. I am able to connect to the target machine on both address with software like Putty and WinSCP and ping it on the command prompt.
Here is the relevant part of my connection method:
// Open socket
WSADATA data;
int err = WSAStartup(MAKEWORD(2, 0), &data);
if (err != 0) return "ERROR: Failed to initialize WSA";
sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
struct sockaddr_in sin;
sin.sin_family = AF_INET;
sin.sin_port = htons(port);
sin.sin_addr.s_addr = to_uint32_t(ip);
if (net::connect(sock, (struct sockaddr*) &sin, sizeof(struct sockaddr_in)) != 0) return "ERROR: Could not connect to host. Code: " + std::to_string(WSAGetLastError());
The variable port is an integer (value = 22), with ip being a string (192.168.1.101 or 72.196.212.127). This function returns the "Could not connect to host" error. No other errors occur.
Here is the to_uint32_t method:
std::uint32_t to_uint32_t(const std::string& ip_address)
{
const unsigned bits_per_term = 8;
const unsigned num_terms = 4;
std::istringstream ip(ip_address);
uint32_t packed = 0;
for (unsigned i = 0; i < num_terms; ++i)
{
unsigned term;
ip >> term;
ip.ignore();
packed += term << (bits_per_term * (num_terms - i - 1));
}
return packed;
}
#selbie pointed out that I was not using the correct function for resolving the IP. To fix my code, I just switched sin.sin_addr.s_addr = to_uint32_t(ip); to inet_pton(AF_INET, ip, &sin.sin_addr);.
Trying to get a program to return an IP address along with a port number so I can create an effective TCP Client/Server program. Struggling with the function getaddrinfo() at the moment and understand that the 2nd argument in the function is what designates the port number. I can get it to return an IP but can't get it to return a port number. I'm inputting the host name and port designation (ex. http or telnet) in string form and trying to get back an IP address and port number associated with it.
I've tried inputting AI_NUMERICSERV into ai.flags in order to input the numeric value of the port number besides specifying "http" and "telnet". Just trying to understand network programming for the first time.
int main(int argc, char **argv){
struct addrinfo hints, *res, *p;
int status;
char ipstr[INET_ADDRSTRLEN];
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
// hints.ai_flags = AI_NUMERICSERV;//leaving this off for now
if((status = getaddrinfo(argv[1], argv[2], &hints, &res)) != 0)
{
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(status));
return 2;
}
`for(p = res; p != NULL; p = p->ai_next)
{
void *addr;
struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr;
addr = &(ipv4->sin_addr);
inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr);
printf("%s\n", ipstr);
}
printf("IP addresses for %s:\n\n", argv[1]); //displays IP correctly
printf("Port for %s: ", argv[2]); // doesn't display port number
freeaddrinfo(res);
return 0;
}
I keep expecting a port number output next to IP address output but I always get just the IP address and not the port number.
You need to read the port(s) returned by res->ai_addr...
printf("port=%h\n", ntohs(((struct sockaddr_in*)(res->ai_addr)) ->sin_port));
If you are just trying to figure out what port(s) are associated with specific services, and you are on a *nix host, you can also just grep /etc/services.
I am using libssh to make my own ssh server (some kind of honeypot). I would like to save the ip address of connected client into my logfile. How to get this IP address? Programming in c++. Thanks in advance guys!
Here is little function I'm using.
string getClientIp(ssh_session session) {
struct sockaddr_storage tmp;
struct sockaddr_in *sock;
unsigned int len = 100;
char ip[100] = "\0";
getpeername(ssh_get_fd(session), (struct sockaddr*)&tmp, &len);
sock = (struct sockaddr_in *)&tmp;
inet_ntop(AF_INET, &sock->sin_addr, ip, len);
string ip_str = ip;
return ip_str;
}
It is based on function "get_client_ip" fromhttps://github.com/PeteMo/sshpot/blob/master/auth.c where is complete SSH honeypot implementation.
s = ssh_get_fd(session);
getpeername(s, ...);
In all the example including Beej's Guide, the IP address is provided in dot notation and then it's fed to ::getaddrinfo(). This post doesn't answer my question.
After which the addrinfo struct is used for socket related functions (e.g. connect(), bind(), listen()). For example:
struct addrinfo hints, *res;
// ... create socket etc.
connect(sockfd, res->ai_addr, res->ai_addrlen);
Example
The variable ai_addr is of type sockaddr which can be safely typecasted to sockaddr_storage, sockaddr_in and sockaddr_in6.
Question:
If I typecast sockaddr to sockaddr_in (or sockaddr_in6)
sockaddr_in& ipv4 = (sockaddr_in&)(sockaddr_variable);
and feed below info:
ipv4.sin_family = AF_INET
ipv4.sin_addr = [IP Address in net byte order]
ipv4.sin_port = [Port number in net byte order]
Can I call the connect() method directly using above info?
connect(sockfd, &ipv4, sizeof(ipv4));
With my program it doesn't appear to work. Am I missing something, or is there a better way?
The motivation behind is that, if we have the information of IPAddress, Port etc. in socket readable format then why to go through the cycle of getaddrinfo()
Be sure you're placing your values in network order, here's a small example:
#include<stdio.h>
#include<sys/socket.h>
#include<arpa/inet.h>
int main(int argc, char *argv[])
{
int sock;
struct sockaddr_in server;
sock = socket(AF_INET, SOCK_STREAM, 0);
if (sock == -1)
{
printf("Could not create socket\n");
}
printf("Socket created\n");
server.sin_family = AF_INET;
// 173.194.32.207 is a google address
server.sin_addr.s_addr = 173 | 194 << 8 | 32 << 16 | 207 << 24;
server.sin_port = 0x5000; // port 80
if (connect(sock, (struct sockaddr *)&server, sizeof(server)) < 0)
{
perror("connect failed. Error");
return 1;
}
printf("Connected\n");
close(sock);
return 0;
}
First check whether the machine is reachable & the server application is running on the machine using "netstat" utility. Use inet_aton method to convert dotted address to network byte order. Finally, log the error value returned by the connect to get the exact reason of failure.
It's worth noting that calling socket::{connect, bind, ...} is wrong: these are C APIs and C doesn't have namespaces, classes and so on.
You should use getaddrinfo as it's much easier and safer to use. But nothing prevents you from using struct sockaddr and all its variants. Indeed, getaddrinfo is a sort of wrapper as stated in man(3) getaddrinfo:
The getaddrinfo() function combines the functionality
provided by the gethostbyname(3) and getservbyname(3) functions into a
single interface, but unlike the latter functions, getaddrinfo() is
reentrant and allows programs to eliminate IPv4-versus-IPv6 dependen‐
cies.
An example:
#include <sys/socket.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
int main()
{
struct sockaddr_in addr = {0};
addr.sin_family = AF_INET;
addr.sin_port = htons(80);
inet_pton(addr.sin_family, "198.252.206.16", &addr.sin_addr);
int fd = socket(addr.sin_family, SOCK_STREAM, 0);
if (fd == -1)
; /* could not create socket */
if (connect(fd, (struct sockaddr *) &addr, sizeof(addr)) == -1)
; /* could not connect */
close(fd);
}
I am working on a server client project on Qt. The server is running in a machine with more than one network interface. The design is such that the client will discover the server automatically. ie the client will broadcast its IP to a network the server get that message and sends back the server's IP. The problem now is that when I try to get the IP in the server, There are more than 1 IP. How to get the IP of the interface through which server have received the message?
This might be a solution for you
IPAddress FindLocalIPAddressOfIncomingPacket( senderAddr )
{
foreach( adapter in EnumAllNetworkAdapters() )
{
adapterSubnet = adapter.subnetmask & adapter.ipaddress;
senderSubnet = adapter.subnetmask & senderAddr;
if( adapterSubnet == senderSubnet )
{
return adapter.ipaddress;
}
}
}
How to get your own (local) IP-Address from an udp-socket (C/C++)
In order to get the incoming peer IP address you can use following solution in C
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);
Getting the source address of an incoming socket connection