UDP Server is binding to the wrong port number - c++

Question

I am attempting to make a very simple UDP client / server setup with non-blocking sockets. I've isolated my problem to the server not binding to the requested Port number and instead binding to one arbitrarily (though it does seem to consistently be the same port).
Is it possible to request a specific port number?
I am attempting to not be IPv4 or IPv6 specific. So I'm not sure if I need to use getaddrinfo if I don't care about the IP address, but I thought that this way it would find whatever was available, or better yet, listen to all IP addresses coming into this port? But it's reporting :: which causes me a problem if I try to tell my clients later what IP address to connect to.
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <Ws2tcpip.h>
#include <cstring>
#include <iostream>
#include <chrono>
#include <iomanip>
#include <sstream>
static uint16_t SERVER_PORT = 56000;
std::wstring get_error_string(const DWORD error)
{
std::wstring returnResult = L"";
LPWSTR errorText = NULL;
FormatMessageW(
FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,
error,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
(LPWSTR)&errorText,
0,
NULL);
if(NULL != errorText)
{
returnResult = errorText;
LocalFree(errorText);
errorText = NULL;
}
std::time_t t = std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
std::tm tm = *std::localtime(&t);
std::wstringstream sstr;
sstr << std::put_time<wchar_t>(&tm, L"%d%m%y %H:%M:%S");
return sstr.str() + L" ERROR (" + std::to_wstring(error) + L"): " + returnResult;
}
std::string convert_to_string(const sockaddr* addr)
{
char* str;
if(addr->sa_family == AF_INET)
{
str = new char[INET_ADDRSTRLEN];
inet_ntop(AF_INET, &(reinterpret_cast<const sockaddr_in*>(addr)->sin_addr), str, INET_ADDRSTRLEN);
}
else
{
str = new char[INET6_ADDRSTRLEN];
inet_ntop(AF_INET6, &(reinterpret_cast<const sockaddr_in6*>(addr)->sin6_addr), str, INET6_ADDRSTRLEN);
}
std::string returnVal = str;
if(addr->sa_family == AF_INET)
returnVal += ":" + std::to_string(reinterpret_cast<const sockaddr_in*>(addr)->sin_port);
else
returnVal = "[" + returnVal + "]:" + std::to_string(reinterpret_cast<const sockaddr_in6*>(addr)->sin6_port);
return returnVal;
}
int main()
{
WSADATA wsaData;
int result = WSAStartup(MAKEWORD(2,2), &wsaData);
if(result != 0)
{
std::wcerr << L"Network init failed: ";
switch(result)
{
case WSASYSNOTREADY:
std::wcerr << L"WSASYSNOTREADY";
break;
case WSAVERNOTSUPPORTED:
std::wcerr << L"WSAVERNOTSUPPORTED";
break;
case WSAEINPROGRESS:
std::wcerr << L"WSAEINPROGRESS";
break;
case WSAEPROCLIM:
std::wcerr << L"WSAEPROCLIM";
break;
case WSAEFAULT:
std::wcerr << L"WSAEFAULT";
break;
default:
std::wcerr << L"Unknown error code " << std::to_wstring(result);
}
std::wcerr << std::endl;
return 0;
}
addrinfo hints = {};
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;
hints.ai_flags = AI_PASSIVE;
addrinfo* serverInfoList;
int status = getaddrinfo(nullptr, std::to_string(SERVER_PORT).c_str(), &hints, &serverInfoList);
if(status != 0)
{
int lastError = WSAGetLastError();
std::wcerr << L"ERROR getaddrinfo: " << get_error_string(lastError) << std::endl;
}
addrinfo* addr = nullptr;
SOCKET sock;
for(addr = serverInfoList; addr != nullptr; addr = addr->ai_next)
{
sock = socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol);
if(sock == INVALID_SOCKET)
{
int lastError = WSAGetLastError();
std::wcerr << L"ERROR socket: " << get_error_string(lastError) << std::endl;
continue; // we'll try the next option
}
u_long blocking = 1;
ioctlsocket(sock, FIONBIO, &blocking);
BOOL conrest = FALSE;
DWORD dwBytesReturned = 0;
WSAIoctl(sock, _WSAIOW(IOC_VENDOR, 12), &conrest, sizeof(conrest), NULL, 0, &dwBytesReturned, NULL, NULL);
int flag = 1;
setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, reinterpret_cast<char*>(&flag), (socklen_t)sizeof(flag));
if(bind(sock, addr->ai_addr, addr->ai_addrlen) == SOCKET_ERROR)
{
int lastError = WSAGetLastError();
std::wcerr << L"ERROR bind: " << get_error_string(lastError) << std::endl;
if(closesocket(sock) == SOCKET_ERROR)
{
lastError = WSAGetLastError();
std::wcerr << L"ERROR closesocket: " << get_error_string(lastError) << std::endl;
}
continue;
}
sockaddr_storage connectedDetails;
std::memset(&connectedDetails, 0, sizeof(connectedDetails));
int addrLen = sizeof(connectedDetails);
if(getsockname(sock, reinterpret_cast<sockaddr*>(&connectedDetails), &addrLen) == SOCKET_ERROR)
{
int lastError = WSAGetLastError();
std::wcerr << L"ERROR getsockname: " << get_error_string(lastError) << std::endl;
}
std::cout << "Connected to " << convert_to_string(reinterpret_cast<sockaddr*>(&connectedDetails)) << std::endl;
break; // we've bound to one of them
}
if(addr == nullptr)
{
std::wcerr << L"ERROR: Could not bind to any addr for localhost port \"" << std::to_wstring(SERVER_PORT) << "\"" << std::endl;
return false;
}
freeaddrinfo(serverInfoList);
while(!(GetAsyncKeyState(VK_ESCAPE) & 0x8000))
{
}
result = WSACleanup();
if(result != 0)
{
std::wcerr << L"Network cleanup failed: ";
switch(result)
{
case WSANOTINITIALISED:
std::wcerr << L"WSANOTINITIALISED";
break;
case WSAENETDOWN:
std::wcerr << L"WSAENETDOWN";
break;
case WSAEINPROGRESS:
std::wcerr << L"WSAEINPROGRESS";
break;
default:
std::wcerr << L"Unknown error code " << std::to_wstring(result);
}
std::wcerr << std::endl;
}
return 0;
}
I'm expecting it to bind to port 56000 but it binds to other ports.

Answer 1

The easiest way is to build the sockaddr_in yourself, since you want to bind to all addresses.
// Create IPv6 UDP socket
X = socket(AF_INET6,SOCK_DGRAM,IPPROTO_UDP);
// Allow both ipv6/ipv4 bind
DWORD ag = 0;
setsockopt(X,IPPROTO_IPV6, IPV6_V6ONLY, (char*)&ag, sizeof(DWORD));
sockaddr_in s = {0};
s.sin_port = htons(SERVER_PORT);
s.sin_family= AF_INET6;
if (bind(X,(sockaddr*)&s,sizeof(s)) == 0) { ... }