I implement asynchronous download to retrieve remote file and store it in IsolatedStorage in order to use it when out of the network.
Everything works great when network is up. However when out of network, I noticed that async donwload may take up to 2 minutes before to fire my MessageBox (which say that connection to server has failed).
Question:
Is there any way to define a timeout ? Let's say that if my application does not receive any answer for X seconds then stop the Async Download and call a method.
Maybe a timeout is not the best pratices. In this case could you give me suggestion ?
I do not want my user wait for 15 seconds max.
PS: my application is suppose to run on wifi only, so I consider that 'network speed' is optimal.
Thx for your help
What I would recommend doing is check the network type first via NetworkInterface. If NetworkInterfaceType is Wireless80211, you have a wireless connection (Wi-Fi). The returned connection can be None in case there is no available way to connect - so you won't even have to start the download if there is no accessible network.
Answering your question, if you are using WebClient, you can't define a timeout. However, you can call instance.CancelAsync(). For a HttpWebRequest you can call instance.Abort().
Related
I am working on a Windows (Microsoft Visual C++ 2005) application that uses several processes
running on different hosts in an intranet.
Processes communicate with each other using TCP/IP. Different processes can be on the
same host or on different hosts (i.e. the communication can be both within the same
host or between different hosts).
We have currently a bug that appears irregularly. The communication seems to work
for a while, then it stops working. Then it works again for some time.
When the communication does not work, we get an error (apparently while a process
was trying to send data). The call looks like this:
send(socket, (char *) data, (int) data_size, 0);
By inspecting the error code we get from
WSAGetLastError()
we see that it is an error 10054. Here is what I found in the Microsoft documentation
(see here):
WSAECONNRESET
10054
Connection reset by peer.
An existing connection was forcibly closed by the remote host. This normally
results if the peer application on the remote host is suddenly stopped, the
host is rebooted, the host or remote network interface is disabled, or the
remote host uses a hard close (see setsockopt for more information on the
SO_LINGER option on the remote socket). This error may also result if a
connection was broken due to keep-alive activity detecting a failure while
one or more operations are in progress. Operations that were in progress
fail with WSAENETRESET. Subsequent operations fail with WSAECONNRESET.
So, as far as I understand, the connection was interrupted by the receiving process.
In some cases this error is (AFAIK) correct: one process has terminated and
is therefore not reachable. In other cases both the sender and receiver are running
and logging activity, but they cannot communicate due to the above error (the error
is reported in the logs).
My questions.
What does the SO_LINGER option mean?
What is a keep-alive activity and how can it break a connection?
How is it possible to avoid this problem or recover from it?
Regarding the last question. The first solution we tried (actually, it is rather a
workaround) was resending the message when the error occurs. Unfortunately, the
same error occurs over and over again for a while (a few minutes). So this is not
a solution.
At the moment we do not understand if we have a software problem or a configuration
issue: maybe we should check something in the windows registry?
One hypothesis was that the OS runs out of ephemeral ports (in case connections are
closed but ports are not released because of TcpTimedWaitDelay), but by analyzing
this issue we think that there should be plenty of them: the problem occurs even
if messages are not sent too frequently between processes. However, we still are not
100% sure that we can exclude this: can ephemeral ports get lost in some way (???)
Another detail that might help is that sending and receiving occurs in each process
concurrently in separate threads: are there any shared data structures in the
TCP/IP libraries that might get corrupted?
What is also very strange is that the problem occurs irregularly: communication works
OK for a few minutes, then it does not work for a few minutes, then it works again.
Thank you for any ideas and suggestions.
EDIT
Thanks for the hints confirming that the only possible explanation was a connection closed error. By further analysis of the problem, we found out that the server-side process of the connection had crashed / had been terminated and had been restarted. So there was a new server process running and listening on the correct port, but the client had not detected this and was still trying to use the old connection. We now have a mechanism to detect such situations and reset the connection on the client side.
That error means that the connection was closed by the
remote site. So you cannot do anything on your programm except to accept that the connection is broken.
I was facing this problem for some days recently and found out that Adobe Acrobat Reader update was the culprit. As soon as you completely uninstall Adobe from the system everything returns back to normal.
I spent a long time debugging a 10054/10053 error in s3 pre-signed uploads
Turns out that the s3 server will reject pre-signed s3 uploads for the first 15 minutes of it's life.
So - If you're debugging s3 check it's not a new bucket.
If you're debugging something else - this is most likely a problem on the server side not client side.
I want to check whether any internet connection is available - i.e can I start webrequests expected to succeed.
IsCellularDataEnabled - is this true if there's GPRS/3G/etc available?
IsNetworkAvailble - is this true if VOICE CALLS are possible, or does this too have something to do with the internet?
IsCellularDataRoamingEnabled - Should I be concerned with this at all? (I know what Data Roaming is...)
IsWifiAvailable - If this false,I can still get internet from 3G.
So what I'm looking for is:
if (/*something*/){ //you can use the internet
}
thanks
(EDIT: I don't have a device readily available, otherwise I'd just try it out :) )
IsNetworkAvailable is true, if there is some kind of data connection available, no matter which (GPRS, 3G, Roaming, WiFi or via USB cable).
IsCellularDataEnabled is true if the phone is connected via a mobile data connection. It doesn't give you any status about Voice calls but only data.
IsCellularDataRoamingEnabled: The user is connected via a mobile data connection via a 3rd provider (roaming). You should only use a minimal amount of traffic because roaming data is often expensive for the user. (Because of that you can check this status)
IsWifiAvailable is true if you are connected via WiFi. If false there may be a mobile data connection via 3G and so on.
So, if you only want to know IF there is some kind of connection you can use IsNetworkAvailable - all other states are only giving you more detailed information about what kind of connection there is.
Only
if(NetworkInterface.GetIsNetworkAvailable()) {
}
http://msdn.microsoft.com/en-us/library/system.net.networkinformation.networkinterface.getisnetworkavailable.aspx
Your question contains a false assumption.
You want to know if there's a connection so your request is likely to succeed. Only the oppostie can be true though. You can only know that if there's no connection a request will definitely fail.
There are lots of reasons that it may not be possible to make a successful web request even if there's a connection to an external network available.
You MUST code to handle a request failing even if there is a connection.
Things that can stop a request from being successful even if there is a connection:
proxy servers or firewalls blocking the request
being connected to a local network which doesn't have access to the destination server
a slow network connection causing the request to timeout
the destination server being down/offline/unavailable
an error on the server
etc. ...
I am in need of a way to decrease the timeout my X server has on remote applications. Currently X11 will keep an application on the display for a very long time (> 30min) after removing the Ethernet connection. I am needing to timeout within 10-30 seconds of loss of communication with the application.
I am running a standard Xorg server with no modification made to it. I have tried numerous methods for doing this. I have tried using the -to option on the X server but this does not seem to have any effect. I have also tried messing with the TCP properties using sysctl. I have set the tcp_keepalive_* properties to values which should give me the timeout needed but this also does not seem to have an effect on the timeout.
Also, the remote applications are not using SSH tunneling to connect to the server. It is an open sever on a secure connection so tunneling is not needed. The timeout mechanism must be done on the server side as I have no control over the applications.
Anyone have any ideas how to get the needed behavior from the X server?
The X server doesn't have client timeouts. Anything you see that looks like one is TCP's doing, not X's.
If you're lucky, the application you're talking to responds to the _NET_WM_PING protocol (most modern toolkits do this for you internally). If you can at least control the window manager you're using, you could modify it to send ping messages to all your running apps and blow them away with XKillClient if they don't respond promptly.
I'm working with an embedded system which has a RAS entry already set up, using the API function RasDial from rasapi32.dll.
All works well except if something goes wrong after RasDial and before RasHangUp. In this case any further attempt to dial is met with error 756 "connection is being dialled", whether the dial attempt is done via the API or via the Windows rasdial command line utility.
rasdial connectionname /d doesn't help either.
The com port used for the modem is locked.
The only way to recover is to reboot.
Obviously under normal circumstances the solution is to make sure that RasDial is always followed by RasHangUp. But for cases where this doesn't happen, is there a way of aborting the dial attempt? For example, if the app calls RasDial and then crashes, how do I get out of that other than by rebooting?
Unfortunately, unless your application can properly terminate the connection that's in progress before exiting the RAS state machine becomes corrupted and must reboot to fix the problem. I've noticed that Windows 7 handles these sorts of scenarios better than XP and Vista did, but there are still occasions when I've had to reboot.
I've managed to prevent most of these sorts of problems with the DotRas API as long as they're occuring in the event handlers of the RasDialer, but if the application crashes from another thread and not from the background thread which raises the RasDialer events, there's nothing I can do about that.
For asynchronous dialing using the DotRas 1.2 SDK:
using DotRas;
RasDialer dialer = new RasDialer();
dialer.EntryName = "My Connection";
dialer.Credentials = new NetworkCredential("My", "User");
dialer.DialAsync();
From this point you can call dialer.DialAsyncCancel() if you want to cancel the connection attempt that's in progress.
For synchronous dialing using the DotRas 1.2 SDK is very similar to asynchronous dialing other than replacing the DialAsync call with simply dialer.Dial().
Here's a link to the API I was talking about: http://www.codeplex.com/DotRas
Hope that helps!
I know about the IsNetworkAlive function from the Windows API but IsNetworkAlive returns false until there's any network activity.
That is, if you start your computer and test connectivity it will return false. If you then ping another computer (or recieve a ping or any network activity from another computer) then it will start returning true.
Is there any alternative or does anyone know a workaround for this?
Things I've tried so far:
Ping to the local host (no go as there isn't really any network activity)
Ping to the local address (the same as before)
Note: I know there's another question very similar to this one, but my problem here is with IsNetworkAlive behaviour
The WinInet functions should meet your needs. Of particular interest is the InternetGetConnectedState function.
Maybe this is what you want: Check network connection status using C#.net?
(It use InternetGetConnectedState WinInet function)
Consider using
NetworkChange Class
The Connection Monitor Application Block