I'm currently working in C# and I need to check the state of the JMS connection that i made (whether it's connected / disconnected). I'm sure that I can connect and disconnect succesfully..its just that i need to display the status of the connection in my UI.
Is there any properties of the JMS connection that states connection status? Or is there any other method that i can use to check the connection status?
Thanks for your help. :)
Currently, I'm using the ExceptionListener to listen for any exceptions and a flag will be set to false when any exception is catched. And when I'm connecting, I will set the flag to true vice versa when i disconnect, I will set the flag to false.
This flag will be used by my UI to detect whether the connection is up or not.
However I was thinking that if theres any property / methods of the IBM connection which can be used to show the state of the connection as its a much better solution. For SonicMQ, theres .getConnectedState() which shows whether the connection is active or inactive. I was wondering whether if IBM have something similar to SonicMQ?
You can use the Connection.setExceptionListener() method to be notified asynchronously of exceptions detected in the connection. If a problem is detected the onException() method is called.
Be sure to set the FAILIFQUIESCE property on the factories and destinations so that your connection is notified and closed in an orderly fashion when the QMgr is shut down by the administrator.
In v7 of WMQ it is possible so enable session reconnection in the transport. In this case, the application may not be aware that the connection was interrupted but you can treat it as having been continuously connected.
Note that, for the most part, exceptions are driven by the application's API calls. So if the connection is lost, you may not know about it in real time but rather find out when an API call is made. If the application sits idle for long periods of time and you want a real-time display of connection status. Please see also "How to find out if JMS Connection is there?" for more on that topic.
WMQ v7 has options to reconnect the client automatically. You must be using v7 at both the client and the server for this to work. Since v6 is end-of-life as of Sept 2011, it is best if you develop this app on v7. You can download the v7 client as SupportPac MQC7. When JMS client reconnect is enabled, the application may not be aware of the connection activity except as a delay in responding to an API call while the connection is rebuilt. The length of that delay depends on channel tuning set by the administrator and in the connection factory.
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I need to implement a dead man's switch in my application. If the application is running from RDP, I need to act if it loses connection to the remote client.
I know when I am running in RDP by using
GetSystemMetrics(SystemMetric.SM_REMOTESESSION)
But when the client closes without signing out, the session will continue. This is the scenario I want to react to, but I don't know how to detect a client disconnecting. I need to know if there is an active RDP user or not.
I could potentially find the remote endpoint by watching the RDP port, but as think could potentially be setup on a non-default port, I'd like to avoid this solution if a better one exists.
I'd prefer a solution that was not specific to WinForms, WPF, UWP etc. Bonus points if it works with .NET Core as well.
Not a .NET Core solution, but a windows API one. There are session change notifications that you can opt into via WTSRegisterSessionNotification (and similarly unregister later).
These notifications are then delivered in your windows message loop, so you need to be running one. (WinForms and WPF do, and there are specific mechanisms to allow you to perform custom message handling)
You'll then get notified when the session becomes locked or disconnected.
I have a c# .net4 application that listens on a socket using BeginReceiveFrom and EndRecieveFrom. All works as expected until I put the machine to sleep and then resume.
At that point EndReceieveFrom executes and throws an exception (Cannot access a disposed object). It appears that the socket is disposed when the machine is suspended but I'm not sure how to handle this.
Do I presume that all sockets have been disposed and recreate them all from scratch? I'm having problems tracking down the exact issue as remote debugging also breaks on suspend/resume.
What happens during suspend/resume very much depends on your hardware and networking setup. If your network card is not disabled during suspend, and the suspend is brief, open connections will survive suspend/resume without any problem (open TCP connections can time out on the other end of course).
However, if your network adapter is disabled during the sleep, or it is a USB adapter that gets disabled because it is connected to a disabled hub, or your computer gets a new IP address from DHCP, or your wireless adapter gets reconnected to a different access point, etc., then all current connections are going to be dropped, listening sockets wil no longer be valid, etc.
This is not specific to sleep/resume. Network interfaces can come up and go down at any time, and your code must handle it. You can easily simulate this with a USB network adapter, e.g. yank it out of your computer and your code must handle it.
I've had similar issues with suspend/resume and sockets (under .NET 4 and Windows 8, but I suspect not limited to these).
Specifically, I had a client socket application which only received data. Reading was done via BeginReceive with a call-back. Code in the call-back handled typical failure cases (e.g. remote server closes connection either gracefully or not).
When the client machine went to sleep (and this probably applies to the newer Windows 8 Fast Start mode too which is really just a kind of sleep/hibernate) the server would close the connection after a few seconds. When the client woke up however the async read call-back was not getting called (which I would expect to occur as it should get called when the socket has an error condition/is closed in addition to when there is data). I explicitly added code on a timer to the client to periodically check for this condition and recover, however even here (and using a combination of Poll, Available and Connected to check if the connection was up) the socket on the client side STILL appeared to be connected, so the recovery code never ran. I think if I had tried sending data then I would have received an error, but as I said this was strictly one-way.
The solution I ended up using was to detect the resume from sleep condition and close and re-establish my socket connections when this occurred. There are quite a few ways of detecting resume; in my case I was writing a Windows Service, so I could simply override the ServiceBase.OnPowerEvent method.
I have a chat site (http://www.pitput.com) that connects user via socket connections.
I have in the client side a flash object that opens a connection to a port in my server.
In the server i have a service that is listening to that port in an async matter.
All is working fine except when i talk to someone after an unknown period of time(about couple of minutes) the server is closing my connection and i get an error in the server :
" A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond".
I dont know how exactly the tcp socket works. does it checking for "live" connection every couple of seconds? how does it decide when to close the connection? Im pretty sure that the close operation is not coming from the client side.
Thanks.
Sounds like the server is handling the connection but not responding. This is the point where I usually pull out WireShark to find out what's going on.
TCP/IP does have an option for checking for live connections; it's called "keepalive." Keepalives are hardly ever used. They're not enabled by default. They can be enabled on a system-wide basis by tweaking the Registry, but IIRC the lowest timeout is 1 hour. They can also be enabled on a single socket (with a timeout in minutes), but you would know if your application does that.
If you are using a web service and your client is connecting to an HTTP/HTTPS port, then it may be getting closed by the HTTP server (which usually close their connections after a couple minutes of idle time). It is also possible that an intermediate router may be closing it on your behalf after an amount of idle time (this is not default behavior, but corporate routers are sometimes configured with such "helpful" settings).
If you are using a Win32 service, then it does in fact sound like the client side is dropping the connection or losing their network (e.g., moving outside the range of a wireless router). In the latter case, it's possible that the client remains oblivious to the fact that the connection has been closed (this situation is called "half-open"); the server sees the close but the client thinks the connection is still there.
Is this an ASP web service hosted with some company? If so, the server generally recycles apps every 10 to 20 minutes. You cannot have a web service running indefinitely, unless it's your own server (I believe).
I have a website using Microsoft SQL 2008 server over local network. Sometimes, SQL server machine is rebooted, and so the website fails to connect to the database. If the machine is up and running, it will respond fast. If it's down, there is no need to wait for 15 seconds. 3 seconds are ok.
I want to display apologizes on the website when the database is not reachable, and want to do it fast. But setting Connection Timeout=3 in connection string seems having no effect. The page spends 22 seconds to wait before throwing SqlException on SqlConnection.Open();.
What's wrong with it? May it be a hidden configuration which overrides the timeout?
Currently, my connection string is
Data Source=...;
Initial Catalog=...;
Integrated Security=True;
Connection Timeout=3
If I set it to ...;ConnectionTimeout=3 (without space),
System.ArgumentException: Keyword not supported: 'connectiontimeout'.
is thrown (strange, MSDN documentation indicates that we can use both strings).
There is a timeout before the networking hardware reports connection timeout to the network drivers, which in turn notifies the programs waiting for network IO. You can verify transport layer timeouts via telnet servername 1433 (assuming your sql server is listening on port 1433).
But 3 seconds is way too short for a process to initialize the network APIs (assuming your web app is in its own application pool), send request and wait for the hardware to timeout. Updating BIOS/firmware/driver probably won't reduce the response time that much.
It would be better to carry out the connection asynchronously. i do not suggest using EndInvoke to end the asynchronous call as unlucky users may still need to wait 3 full seconds to see any response when the database is down. Maybe an Ajax call is better. If you have a lot of users constantly hitting your web site, you may want to cache the result of connectivity checking and update it in a manner meaningful to your users.
The following blog post assisted me in solving this problem:
http://improve.dk/controlling-sqlconnection-timeouts/
ConnectionTimeout without space is the property name when accessing via code, not for the connection string.
Not sure if this is of use, but when I hit this issue in the past, it was because I also needed to set SqlCommand.CommandTimeout. What happened for me is the connection was opened successfully, then DB server went down, then my next command did not timeout as quickly as I expected based on the Connection Timeout, and this was due to the CommandTimeout needing to be set as well.
I have a windows service written in C# .NET framework 3.5 and would like to know the best way to check if previous shutdown of a service was regular.
Upon starting the service, there should be a check if the last shutdown was regular (via stop service button in services management) or if somebody just killed the process (or it crashed for some reason not directly linked to the service itself).
I thought about writing encrypted XML on a hard drive upon starting a service, and then editing it with some values when service is being stopped. In that way, after I start the service again next time, I could check the XML and see if the values were edited in correct way during shutdown, and if they were not I'd know the process was killed or it crashed.
This way seems too unreliable and not a good practice. What do you suggest?
Clarification:
What the service does is it sits on a server and listens to connections from client machines. Once the connection has been established, it communicates to a remote database via web services and determines whether they have right to connect (and therefore use application that is the caller). One of the aspects of protection is concurrency check, and if I have a limit set to 5 work stations, I keep the TcpClient connection alive from windows service to, let's say 5 workstations, and the sixth one cannot connect.
If I kill the service process and restart it, the connections are gone and I have 5 "licensed" apps running on workstations, and now there are 5 free connection slots to be taken by 5 more.
I also cant see anything bad using a file. You could even use this file to log some more information.
Eg. you could attach to the AppDomains Unhanded Exception event and try to log that exception.
Or you could evaluate how log your service has been running/not running (parsing a logfile for that task is a little bit harder).
Of course - this is not an excuse for not using logfiles.
I went with this in the end:
Service used to check up on the connected workstations to see if they're alive, but now I've built in periodical check from all the workstations as well (they connect through a common router dll where I've built in the check). Every 10 seconds the connection is verified, and if there is none, the client will try to reconnect in 15 seconds, which will be successful if there was just a temporary network problem, but will fail if the service was shut down forcefully (since all it's Tcp objects will be lost).
I would suggest to use the EventLog. Add a log event when a service start or stops and read through the event logs to detect anomalies.
Here's a basic sample from CodeProject.
Here's a walkthrough from MSDN how to create/delete/read event logs and entries.
Unless the service is running some sort securiy system that you need to have a "tamper" proof system i dont see why using a file is a bad solution.
Personaly i think a encrpted xml file is overkill, a simple text file should be enough.
I think you are on the right track, I'm not sure why you want to edit the values, just use the file (or a registry key) as a marker to indicate that the service was started and is running. During a graceful shutdown remove the marker. You then just need to look for the existence of the marker to know whether you were shutdown gracefully or crashed.
If you are finding that the file isn't created reliably, then make sure you are closing and flushing and disposing of the file object rather than relying on the garbage collector.
--- EDIT following clarification ---
So the requirement is for a licensing system and not simply to determine if the service was shutdown gracefully. I'm guessing that the desire is for the 'licenses' to be cleared on a graceful shutdown and restored following a crash, the scenarios are interchangeable.
I would probably use a database backing store, with suitable security, to hold the license keys at the server. As each client connects and requests a license they are provided with a key that has to be presented for each communication from the client. The server is obviously verifying that the presented key is valid for the current session. Should the server be gracefully shutdown it can clear the key table, if it crashes then the keys would still be present and can be honoured. That's probably the simplest approach I can think of that's secure.
If there's yet more to the story then let us know.