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Deferring DNS resolution until connection attempt #121

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Deferring DNS resolution until connection attempt #121

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70 changes: 37 additions & 33 deletions M2Mqtt/Net/MqttNetworkChannel.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,6 @@ public class MqttNetworkChannel : IMqttNetworkChannel
#endif
// remote host information
private string remoteHostName;
private IPAddress remoteIpAddress;
private int remotePort;

// socket for communication
Expand All @@ -66,7 +65,41 @@ public class MqttNetworkChannel : IMqttNetworkChannel
/// <summary>
/// Remote IP address
/// </summary>
public IPAddress RemoteIpAddress { get { return this.remoteIpAddress; } }
public IPAddress RemoteIpAddress
{
get
{
try
{
// Check if remoteHostName is a valid IP address and get it
return IPAddress.Parse(remoteHostName);
}
catch
{
}

// In this case the parameter remoteHostName isn't a valid IP address
IPHostEntry hostEntry;
try
{
hostEntry = Dns.GetHostEntry(remoteHostName);
}
catch (Exception e)
{
throw new Exception("Failed to resolve the remote host name", e);
}

// check for the first address not null
// it seems that with .Net Micro Framework, the IPV6 addresses aren't supported and return "null"
foreach (IPAddress address in hostEntry.AddressList)
{
if (address != null)
return address;
}

throw new Exception("No address found for the remote host name");
}
}

/// <summary>
/// Remote port
Expand Down Expand Up @@ -180,36 +213,7 @@ public MqttNetworkChannel(string remoteHostName, int remotePort, bool secure, X5
public MqttNetworkChannel(string remoteHostName, int remotePort, bool secure, X509Certificate caCert, X509Certificate clientCert, MqttSslProtocols sslProtocol)
#endif
{
IPAddress remoteIpAddress = null;
try
{
// check if remoteHostName is a valid IP address and get it
remoteIpAddress = IPAddress.Parse(remoteHostName);
}
catch
{
}

// in this case the parameter remoteHostName isn't a valid IP address
if (remoteIpAddress == null)
{
IPHostEntry hostEntry = Dns.GetHostEntry(remoteHostName);
if ((hostEntry != null) && (hostEntry.AddressList.Length > 0))
{
// check for the first address not null
// it seems that with .Net Micro Framework, the IPV6 addresses aren't supported and return "null"
int i = 0;
while (hostEntry.AddressList[i] == null) i++;
remoteIpAddress = hostEntry.AddressList[i];
}
else
{
throw new Exception("No address found for the remote host name");
}
}

this.remoteHostName = remoteHostName;
this.remoteIpAddress = remoteIpAddress;
this.remotePort = remotePort;
this.secure = secure;
this.caCert = caCert;
Expand All @@ -226,9 +230,9 @@ public MqttNetworkChannel(string remoteHostName, int remotePort, bool secure, X5
/// </summary>
public void Connect()
{
this.socket = new Socket(this.remoteIpAddress.GetAddressFamily(), SocketType.Stream, ProtocolType.Tcp);
this.socket = new Socket(this.RemoteIpAddress.GetAddressFamily(), SocketType.Stream, ProtocolType.Tcp);
// try connection to the broker
this.socket.Connect(new IPEndPoint(this.remoteIpAddress, this.remotePort));
this.socket.Connect(new IPEndPoint(this.RemoteIpAddress, this.remotePort));

#if SSL
// secure channel requested
Expand Down