public async Task <IPEndPoint> ResolveAsync(string endpoint, int port, IpVersion ipVersion = IpVersion.IpV4, CancellationToken token = default(CancellationToken))
{
string cacheKey = $"{endpoint}:{port}:{ipVersion}";
if (port < IPEndPoint.MinPort || port > IPEndPoint.MaxPort)
{
throw new ArgumentOutOfRangeException(nameof(port));
}
if (cache.HasKey(cacheKey))
{
return(cache.Get <IPEndPoint>(cacheKey));
}
var addressFamily = ipVersion.HasFlag(IpVersion.IpV4)
? AddressFamily.InterNetwork
: AddressFamily.InterNetworkV6;
token.ThrowIfCancellationRequested();
IPEndPoint ipEndpoint;
var ipAddress = TryGetIpAddress(endpoint);
if (ipAddress != null)
{
ipEndpoint = new IPEndPoint(ipAddress, port);
cache.Add(cacheKey, ipEndpoint, TimeSpan.FromMinutes(60));
return(ipEndpoint);
}
try
{
#if NET40
var allAddresses = Dns.GetHostAddresses(endpoint);
#else
var allAddresses = await Dns.GetHostAddressesAsync(endpoint);
#endif
var firstAddressInFamily = allAddresses.FirstOrDefault(x => x.AddressFamily == addressFamily);
if (firstAddressInFamily != null)
{
ipEndpoint = new IPEndPoint(firstAddressInFamily, port);
cache.Add(cacheKey, ipEndpoint, TimeSpan.FromMinutes(60));
return(ipEndpoint);
}
if (addressFamily == AddressFamily.InterNetwork && ipVersion.HasFlag(IpVersion.IpV6))
{
ipEndpoint = await ResolveAsync(endpoint, port, IpVersion.IpV6, token);
if (ipEndpoint != null)
{
cache.Add(cacheKey, ipEndpoint, TimeSpan.FromMinutes(60));
return(ipEndpoint);
}
}
var firstAddress = allAddresses.FirstOrDefault();
if (firstAddress == null)
{
return(null);
}
switch (firstAddress.AddressFamily)
{
case AddressFamily.InterNetwork:
#if NET40
ipEndpoint = new IPEndPoint(firstAddress, port);
#else
ipEndpoint = new IPEndPoint(firstAddress.MapToIPv6(), port);
#endif
break;
case AddressFamily.InterNetworkV6:
#if NET40
ipEndpoint = new IPEndPoint(firstAddress, port);
#else
ipEndpoint = new IPEndPoint(firstAddress.MapToIPv4(), port);
#endif
break;
default:
return(null);
}
cache.Add(cacheKey, ipEndpoint, TimeSpan.FromMinutes(60));
return(ipEndpoint);
}
catch
{
return(null);
}
}
