I'm developing an application for Honeywell Dolphin 6100, a mobile computer with a barcode scanner that uses Windows CE 5.0 like OS.
I want to use a function which can check the network connection existence, I tried to use the code below but its too slow.
public static bool CheckForInternetConnection()
{
string url = "http://www.Microsoft.com/";
try
{
System.Net.WebRequest myRequest = System.Net.WebRequest.Create(url);
System.Net.WebResponse myResponse = myRequest.GetResponse();
}
catch (System.Net.WebException)
{
return false;
}
return true;
}
Any one have an idea for a faster way to do that. I mention that I'm working with VS2008 on win7
Since you're not doing anything with the content of the response, there's really no reason to request it, and wait for the network transfer of all that data. You might try setting myRequest.Method = "HEAD", which will just return headers (assuming the web server supports it), but obviously still verify that you can communicate with the remote web server.
http://msdn.microsoft.com/en-us/library/system.net.httpwebrequest.method.aspx
Assuming availability on your version of the .net runtime, you can call the static System.Net.NetworkInformation.GetIsNetworkAvailable() method. There are scenarios where that'll return true and you won't be able to route to the outside world, but it'll tell you whether your device has a network interface that's marked as being up.
Related
We like to enable some hidden features of our software only if it is run inside of the company network. The key requirements are:
no need for a third party library outside of DotNet 4.5.1
easy to implement (should not be more than some dozens of lines .. I don't want to reimplement a crypto library)
It should be reasonable safe:
at least: hard to reverse engineer
at best: "impossible" to break even with read-access to the source code
low maintenance overhead
Win2012-Server is available for installation of additional software (open source or own implementation prefered - server can be assumed to be safe)
What I have thought about:
Check if a specific PC is available with a known MAC or IP (current implementation, not really secure and some other flaws)
Test, if a service is available on a specific response (i.e. I send 'Hello' to MyServer:12345 - server responses with 'World')
Similar to 2nd but a more complex challenge (i.e. send a seed for a RNG to the server, verify the response)
Set up an apache with HTTPS and verify the certificate
If you use ActiveDirectory, you could add a reference to the System.DirectoryServices namespace and check
ActiveDirectorySite currentSite = ActiveDirectorySite.GetComputerSite();
then you can get a bit of information from the currentSite object and check against that. That's how I enable/disable features of an application I'm developing currently.
I also grab:
var client = Dns.GetHostEntry(Dns.GetHostName());
foreach (var ip in client.AddressList)
{
if(ip.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
{
ipAddress = ip;
}
}
Which you can check to make sure the client is connected with the proper protocol.
I've choosen the last option: Set up a webserver in the intranet and verify the certificate.
It was easier than expected. There are enough tutorials for setting up an apache with https for every supported OS. The self-signed certificate have a lifetime of 9999 days - should be okay until 2042. The C#-part is also reasonable small:
private static bool m_isHomeLocation = false;
public static bool IsHomeLocation
{
get
{
if (m_isHomeLocation)
return true;
try
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://yourLicenseServer:yourConfiguredPort");
request.ServerCertificateValidationCallback += ((s, certificate, chain, sslPolicyErrors) => true);
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
response.Close();
var thumbprint = new X509Certificate2(request.ServicePoint.Certificate).Thumbprint;
m_isHomeLocation = (thumbprint == "WhateverThumbprintYourCertificateHave");
}
catch
{
// pass - maybe next time
}
return m_isHomeLocation;
}
}
How can i check if a method in a web service is working fine or not ? I cannot use ping. I still want to check any kind of method being invoked from the web service by the client. I know it is difficult to generalize but there should be some way.
I use this method and it works fine :
public bool IsAddressAvailable(string address)
{
try
{
System.Net.WebClient client = new WebClient();
client.DownloadData(address);
return true;
}
catch
{
return false;
}
}
The only way to know if a web service method is working "fine" is to call the method and then to evaluate whether the result is "fine". If you want to keep a record of "fine" vs. time, then you can log the result of the evaluation.
There's no more general way to do this that makes any sense. Consider:
You could have code that creates an HTTP connection to the service endpoint, but success doesn't tell you whether the service will immediately throw an exception as soon as you send it any message.
You could connect and send it an invalid message, but that doesn't tell you much.
You could connect and send it a valid message, then check the result to ensure that it is valid. That will give you a pretty good idea that when a real client calls the service immediately afterwards, the real client should expect a valid result.
Unless the service takes that as an opportunity to crash, just to spite you!
The best technique would be to use WCF tracing (possibly with message-level tracing) to log what actually happens with the service, good or bad. A human can then look at the logs to see if they are "fine".
Powershell is by far an easy way to 'ping' a webservice endpoint.
Use the following expression:
Test-NetConnection -Port 4408 -ComputerName 192.168.134.1
Here is a failure response for a port that does not exist or is not listening;
WARNING: TCP connect to 192.168.134.1:4408 failed
ComputerName : 192.168.134.1
RemoteAddress : 192.168.134.1
RemotePort : 4408
InterfaceAlias : Ethernet0
SourceAddress : 192.168.134.1
PingSucceeded : True
PingReplyDetails (RTT) : 0 ms
TcpTestSucceeded : False
Here is a success result if the address/port is listening and accessible:
ComputerName : 192.168.134.1
RemoteAddress : 192.168.134.1
RemotePort : 4407
InterfaceAlias : Ethernet0
SourceAddress : 192.168.134.1
TcpTestSucceeded : True
just use try catch inside the method of your webservice and log exceptions to a log file or to the event log.
Example:
[OperationContract]
public bool isGUID(string input)
{
bool functionReturnValue = false;
try
{
Guid guid;
functionReturnValue = Guid.TryParse(input, guid);
}
catch (Exception ex)
{
Log.WriteServerErrorLog(ex);
}
return functionReturnValue;
}
You don't need to ping the webservice, but instead ping the server with a watchdog service or something. There is no need to "ping" the webservice. I also think you don't need to do this anyway.
Either your webservice works or it doesn't because of bad code.
You may try curl. It's a Linux tool, should be there in Cygwin too.
$ curl http://google.com
<HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8">
<TITLE>301 Moved</TITLE></HEAD><BODY>
<H1>301 Moved</H1>
The document has moved
here.
</BODY></HTML>
There are lots of options; examples can be found in the 'net.
You can write your self a little tool or windows service or whatever you need then look at these 2 articles:
C#: How to programmatically check a web service is up and running?
check to if web-service is up and running - efficiently
EDIT:
This was my implementation in a similar scenario where I need to know if an external service still exists every time before the call is made:
bool IsExternalServiceRunning
{
get
{
bool isRunning = false;
try
{
var endpoint = new ServiceClient();
var serviceUri = endpoint.Endpoint.Address.Uri;
var request = (HttpWebRequest)WebRequest.Create(serviceUri);
request.Timeout = 1000000;
var response = (HttpWebResponse)request.GetResponse();
if (response.StatusCode == HttpStatusCode.OK)
isRunning = true;
}
#region
catch (Exception ex)
{
// Handle error
}
#endregion
return isRunning;
}
}
As I see it, you have 2 options:
If you can access the server it is running on, Log every call (and exceptions thrown). Read the log file with a soft like baretail that updates as the file is being written.
If you can't access the server, then you have to make the webservice write that log remotely to another computer you have access to.
Popular loggers have this functionality built in. (Log4Net, ...)
You could also use tracing.
http://msdn.microsoft.com/en-us/library/ms732023.aspx
http://msdn.microsoft.com/en-us/library/ms733025.aspx
I have a WM 6.1 Prof. application that checks updates when user wishes to do so.
I want to check if there is any avaliable connection (GPRS or Wifi) before it attempts to connect to server.
I am also using openNETCF.NET dll here is what I have done but it doesn't work everytime,
also I am not sure which type of connection should I use and so.
Ok do you think is this good?
Thank you very much!
private static HttpWebRequest ConnectWeb(string urlx)
{
try
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(new Uri(urlx));
request.ContentType = #"application/octet-stream";
request.Credentials = CredentialCache.DefaultCredentials;
request.Timeout(6000);
return request;
}
catch (Exception ex)
{
MessageBox.Show(Lang.CONNECTIONPROBLEM);
return null;
}
}
private bool downloadTest()
{
Stream stream;
HttpWebResponse response;
HttpWebRequest request = ConnectWeb(FileManager.url);
if (request!=null)
{
try
{
using (response = (HttpWebResponse)request.GetResponse())
{
using (stream = response.GetResponseStream())
{
byte[] data = ReadFully(stream, (int)response.ContentLength);
writeByteArrayToFile(data, "data.zip");
}
}
response.Close();
stream.Close();
}
catch (Exception ex)
{
MessageBox.Show(Lang.CONNECTIONPROBLEM);
return false;
}
}
Don't disconnect your connection manager.
As soon as you use the Windows Mobile Connection Manager, a plug-in to the network stack (the Autobind Winsock Layered Service Provider) starts automatically binding your network connections to the network interface corresponding to the chosen destination. Basically, it forces the packets to go the right way. If you request a disconnection, it may not send them at all.
Instead you should call Connect before you try to connect to your update server, then RequestDisconnect once you're done with it. Use an Asynchronous connection and attach to the Connected event if you want it to work in the background.
To follow what IE does with choosing the correct destination - WiFi or GPRS - use ConnectionManager.MapUrl to determine the destination GUID, and pass that into Connect. The default mapping behaviour is:
If the server-name part of the URL has no dots, it's a Work address
If the server-name part appears in the list of Exceptions, it's a Work address
Otherwise, it's an Internet address
What it then does depends on how ActiveSync/Windows Mobile Device Center is set up, if the device is cradled, and what is selected under 'My network card connects to', for WiFi (Start > Settings > Connections tab > Network Cards or WiFi icon). If this is set to 'Work' and the mapping is 'The Internet' it will never use WiFi. If it's set to 'The Internet' it will use WiFi if that is associated and fall back to GPRS if not.
As I recall, .NET CF's HttpWebRequest will automatically make use of the Connection Manager, following IE's behaviour of mapping the destination, so you may not need the OpenNETCF class at all.
What is the easiest way to check whether internet connection is available programatically?
EDIT:
As suggested I tried using the following method, but it is always returning true.
[Flags]
enum InternetConnectionState : int
{
INTERNET_CONNECTION_MODEM = 0x1,
INTERNET_CONNECTION_LAN = 0x2,
INTERNET_CONNECTION_PROXY = 0x4,
INTERNET_RAS_INSTALLED = 0x10,
INTERNET_CONNECTION_OFFLINE = 0x20,
INTERNET_CONNECTION_CONFIGURED = 0x40
}
class Program
{
[DllImport("WININET", CharSet = CharSet.Auto)]
static extern bool InternetGetConnectedState(ref InternetConnectionState lpdwFlags, int dwReserved);
static void Main(string[] args)
{
InternetConnectionState flags = 0;
bool isConnected = InternetGetConnectedState(ref flags, 0);
Console.WriteLine(isConnected);
//Console.WriteLine(flags);
Console.ReadKey();
}
}
Additional Info (if it helps): I access internet over a shared wifi network.
Here is the Windows API you can call into. It's in wininet.dll and called InternetGetConnectedState.
using System;
using System.Runtime;
using System.Runtime.InteropServices;
public class InternetCS
{
//Creating the extern function...
[DllImport("wininet.dll")]
private extern static bool InternetGetConnectedState( out int Description, int ReservedValue );
//Creating a function that uses the API function...
public static bool IsConnectedToInternet( )
{
int Desc ;
return InternetGetConnectedState( out Desc, 0 ) ;
}
}
here is the best solution I found so far:
public static bool isConnected()
{
try
{
string myAddress = "www.google.com";
IPAddress[] addresslist = Dns.GetHostAddresses(myAddress);
if (addresslist[0].ToString().Length > 6)
{
return true;
}
else
return false;
}
catch
{
return false;
}
}
usage:
if(isConnected())
{
//im connected to the internet
}
else
{
//not connected
}
Microsoft windows vista and 7 use NCSI (Network Connectivity Status Indicator) technic:
NCSI performs a DNS lookup on www.msftncsi.com, then requests http://www.msftncsi.com/ncsi.txt. This file is a plain-text file and contains only the text 'Microsoft NCSI'.
NCSI sends a DNS lookup request for dns.msftncsi.com. This DNS address should resolve to 131.107.255.255. If the address does not match, then it is assumed that the internet connection is not functioning correctly.
You can check for a network connection using this in .NET 2.0+
System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable();
This will probably just return true for local networks, so it may not work for you.
This is a question where the answer really is "it depends". Because it depends on why you want to check and for what kind of connectivity? Do you want to be able to access certain websites/services over http? Send smtp mail? Do dns lookups?
Using a combination of the previous answers is probably the way to go - first use the wininet api from colithium's answer to check if a connection of any kind is available.
If it is, try a couple of dns lookups (see System.Net.Dns ) for either the resources you're interested in or some popular big websites (google, altavista, compuserve, etc...).
Next, you can try pinging (see Roger Willcocks' answer) and/or establishing a socket connection to the same sites. Note that a failed ping could just mean that firewall rules don't allow you to ping.
If you can be more specific as to why you want to check it will be easier to provide an answer that covers your requirements...
Easiest way is to probably check if they can download a file from the web that you know is available. Use the following code to download google's homepage.
WebClient Client = new WebClient ();
String Response;
Response = Client.DownloadString("http://www.google.com");
You should probably wrap that in a Try .... Catch to catch the exception that is thrown when it can't establish a connection.
Network Awareness in Windows XP
Network Awareness in Windows Vista and Windows 7
Of course this does not guarantee the web site you plan to visit is not blocked by cooperative firewall rules, the API just checking if a pre-defined web site is reachable.
There are some other options too.
The InfoPath library exposes the "IsDestinationReachable" method, which is a wrapper for the Win API method of the same name. (Looks like Vista doesn't support it)
However, I believe from the Docs that it depends on something like PING, so not necessarily a good test.
Vista + say use the "Network List Manager"
#colithium Google might not be down, but things can also fail out if the DNS lokup interval exceeds the timeout. Not uncommon at home here in NZ, first try fails, second succeeds because the data has propogated back to the ISP DNS or your router cache by the time the second request is done.
Alternatively you can use DNS lookup to check internet connectivity. This method is faster than Ping method.
public static bool DnsTest()
{
try
{
System.Net.IPHostEntry ipHe =
System.Net.Dns.GetHostByName("www.google.com");
return true;
}
catch
{
return false;
}
}
We're working on a wrapped WebBrowser component. We'd like to display one page (e.g. oursite.com/thispage.html) if the user is online and another page (e.g. C:\somewhere\thispage_offline.html) if the user is offline. I'm able to to properly display both pages, but my issue is detecting the online/offline status.
I tried
WebBrowser.IsOffline; however it seems that only relays the Offline Mode status, not whether or not the computer is actually able to reach the internet.
Is there a way to detect this from the WebBrowser component? Is there a way at all?
Thanks for all your help!
The simplest way to check for internet connectivity is to ping your server.
Try this code:
public static bool IsOnline() {
var pinger = new Ping();
try {
return pinger.Send("oursite.com").Status == IPStatus.Success;
} catch(SocketException) { return false; } catch(PingException) { return false; }
}
Alternatively, you can try using the WebRequest class to send a request to a simple page on your site and see whether it succeeds. This is a better option because it will also make sure that IIS (or Apache) is running on the server.
What if you just used the Ping class to see if the site is available?