I am using Delphi 11 FMX to write for Linux and Windows.
I have an auto-ping program working well on both platforms, using TIdIcmpClient.
But now, I want to write a program that will ping up to four different IP addresses, displaying a flag when an address goes down. I could, of course, ping one IP and then change the IP and ping another. But I have seen that the first ping is always longer, although I have usually pinged in seconds of interval, once every 5 seconds, for example. The first ping is always much higher than the rest. So, in my program, I ignore the first ping.
I am afraid that if I use one TIdIcmpClient, changing IPs before every ping, it will always be a first ping, and so will not represent the real round trip time. Or does this happen just the first time the TIdicmpClient pings?
Alternately, perhaps I should use multiple TIdIcmpClient components? But I don't know if it is okay to use multiple TIdIcmpClients. This program would ping each address perhaps once every 10 seconds at most, more likely once a minute.
I am looking for advice that will save me time when I write this program. I searched for this on StackOverflow, and elsewhere. I found some useful things here, but nothing this specific.
Related
For the project I'm working on, I need to be able to measure the total amount of network traffic for a specific container over a period of time. These periods of time generally are about 20 seconds, and the precision needed realistically is only in kilobytes. Ideally this solution would not involve the use of additional software either in the containers or on the host machine, and would be suitible for linux/windows hosts.
Originally I had planned to use the 'NET I/O' attribute of the 'docker stats' command, though the field is automatically formatted to a more human readable format (i.e. '200 MB') which means for containers that have been running for some time, I can't get the precision I need.
Is there any way to get the raw value of 'NET I/O' or to reset the running count? Outside of this I've explored using something tshark or iptables, but like I said above ideally the solution would not require additional programs. Though if there aren't any good solutions that fit that criteria any other suggestions would be welcome. Thank you!
I need to synch audio in networked devices with millisecond accuracy. I've hacked together something that works quite well, but is'nt perfectly reliable :
1)Server device sends an rpc with a timeSinceClick param
2)client device launches the same click offsetted according to the time the rpc spent in transit,
3)System.Diagnostics.StopWatch checks periodicaly on all connected devices to make sure playback hasn't deviated too much from absolute time and corrects if necessary
Are there any more elegant ways to do this? Also, my way of doing it requires manual synching if non iOS devices are added to the mix : latency divergences make it very hard to automate...
I'm all eyes!
Cheers,
Gregzo
It is difficult to synchronize multiple devices on the same machine with millisecond accuracy, so if you are able to do this on multiple machines I would say you are doing well. I'm not familiar enough with iOS to the steps you describe, but I can tell you how I would approach this in cross-platform way. Maybe your approach amounts to the same thing.
one machine (the "master") would send a UDP packet with to all other machines.
all other machines would reply as quickly as possible.
the time it takes to receive the reply, divided by two, would be (approximately) the time it takes to get a packet from one machine to another. (this would have to be validated. maybe it takes much longer to process and send a packet? probably not)
after repeating steps 1-3, ignoring any extreme values and averaging the remaining results, you know about how long it takes to get a message from one machine to another.
now "sync" UDP packets can be sent from the main machine to the "slave" machines. The sync packets will include delay information so that when the save machine receive the packets, they know they were sent x milliseconds ago. Several sync packets may need to be sent in case the network delays or drops some of them.
The logs don't show anything different, and the computer is four times faster than the last one. Anyone know any common reasons why making a request to localhost would take a very long time?
I am using Mongrel.
Hard to give a solution based on the little information you give, so try to narrow it down. I would say that these three causes seem the most likely:
the database is slow. You can check this if your queries take a long time (check the logs). Perhaps you are using a slow connector (i.e. the default Ruby MySQL library), or your indexes haven't made it to your new machine.
Mongrel is slow. Check by starting it with Webrick and see if that's any better
your computer is slow. Perhaps it's running something else that's taking up CPU or memory. See your performance monitor (application to use for this differs per OS).
Could be a conflict between IPv4 and IPv6. If you're running Apache you have to take special steps to make it work nicely with IPv6 (my information here might be out of date.) I've found that an IPv6-enabled client would try to talk IPv6 to the server, and Apache would not receive the request. After it timed out the client would retry on IPv4.
is it easy to write a script to test whether the network is ever down for the next 24 or 48 hours? I can use ssh to connect to a shell and come back 48 hours later to see if it is still connected to see if the network has ever been down, but can i do it programmatically easily?
The Internet (and your ethernet) is a packet-switched network, which makes the definition of 'down' difficult.
Some things are obvious; for example, if your ethernet card doesn't report a link, then it's down (unless you have redundant connections). But having a link doesn't mean its up.
The basic, 100 mile view of how the Internet works is that your computer splits the data it wants to send into ~1500-byte segments called packets. It then, pretty much blindly, sends them on their way, however your routing table says to. Then that machine repeats the process. Eventually, through many repetitions, it reaches the remote host.
So, you may be tempted to define up as the packet reached its destination. But, what happens if the packet gets corrupted, e.g., due to faulty hardware or interference? The next router will just discard it. Ok, that's fine, you may well want to consider that down. What if a router on the path is too busy, or the link it needs to be sent on is full? The packet will be dropped. You probably don't want to count that as down.
Packets routinely get lost; higher-level protocols (e.g., TCP) deal with it and retransmit the packet. In fact, TCP uses the packet drop on link full behavior to discover the link bandwidth.
You can monitor packet loss with a tool like ping, as the other answer states.
If your need is more adminstrative in nature, and using existing software is an option, you could try something like monit:
http://mmonit.com/monit/
Wikipedia has a list of similar software:
http://en.wikipedia.org/wiki/Comparison_of_network_monitoring_systems
You should consider also whether very short outages need to be detected. Obviously, a periodic reachability test cannot guarantee detecting outages shorter than the testing interval.
If you only care about whether there was an outage, not how many there were or how long they lasted, you should be able to automate your existing ssh technique using expect pretty easily.
http://expect.nist.gov/
Most platforms support a ping command that can be used to find out if a network path exists to an IP address somewhere "else". Where, exactly, to check depends on what you are really trying to answer.
If the goal is to discover the reliability of your first hop to your ISP's network, then pinging a router or their DNS regularly might be sufficient.
If your concern is really the connection to a single node (your mention of leaving an ssh session open implies this) then just pinging that node is probably the best idea. The ping command will usually fail in a way that a script can test if the connection times out.
Regardless, it is probably a good idea to check at a rate no faster than once a minute, and slower than that is probably sufficient.
I'm using the UPS service to monitor the state of my UPS from an application -- the key at HKLM\SYSTEM\CCS\Services\UPS\Status has all the information you can get from the Power control panel. BUT -- I'd like to be able to tell the UPS to shut down from my app as well. I know that the service can tell the UPS to shut down -- for instance, after running a set number of minutes on battery -- and I'm wondering if there's some kind of command I can send to the service to initiate a shutdown manually.
I'm having trouble searching for this information -- people tend to misspell "Uninterruptible" (hrm, Firefox red-lined that but doesn't have an alternative) and "UPS" just gets hits for the shipping service. Maybe I can do something through System.ServiceController, or WMI?
CLARIFICATION: Yes, I am talking about powering down the physical UPS device. I know how to stop the service. I figured it would be a common problem -- I want my UPS to turn off with the PC. I had an idea I'm going to try, based on this page. You see, APC (and everybody else) has to supply a DLL for the UPS service to call, and since the function calls are well documented, there's no reason I shouldn't be able to P/Invoke them. I'll re-edit this once I know whether or not it worked.
Update: I tried invoking UPSInit, then UPSTurnOff, and nothing happens. I'll tinker with it some more, but the direct call to apcups.dll might be a dead end.
Check my comments to Herman, you want to shut the UPS down, not the UPS SERVICE, correct? I mean, you want that thing to shut off, kill the power, etc, right?
If so, you are looking it on a UPS by UPS model. I doubt two of them would work the same.
In your searches, instead of UPS, try "APC", or "battery". I think a lot of the code is what runs on laptops to deal with being on battery, etc...
Some place hidden in some dusty old files I have protocol information for APC UPS's, and the commands they respond to, and what they send to the PC etc. But this was WAY back in the day when we used to connect our UPS's to our computers with SERIAL cables... You could actually talk to a UPS with Qmodem or Hyperterm...
Learned it from talking to the guys at APC. They are very nice, and helpful. Now-a-days, I think you just post a URL coming from your Powerchute software, and it will talk directly to the UPS, and carry out your commands.
OK, I have the answer (tested!), but it's not pretty. My APC UPS communicates using the APC "Smart" protocol (more here). What you need in my case is a "soft shutdown", "S" command. But first you need to make sure it's in "Smart" mode ("Y"). Now, if you want to let the Windows UPS service monitor state, the service will have an iron grip on the COM port. So you can either a) let the Windows service turn the UPS off, or b) kill the service and turn the UPS off yourself.
The UPS itself has a "grace period" after it gets the "S" command, giving you time to shut down your OS. This means that to do (a) above, you have to:
Kill utility (mains) power
Wait for the Windows UPS Service timeout (default and minimum 2 minutes)
Wait for Windows to shut down -- right near the end, it will send the "S" command
Wait for the UPS grace period, after which it will actually turn itself off
I think we're going to opt for (a), just because (b) involves extra work killing the service and implementing the serial comms.
Please, tell in what language are you trying to do that... if you're using .NET you can do that with ServiceController class (read the docs).
For controlling services in Win32 API using C/C++, Service Functions (Windows).
For example to stop a service you can use ControlService function as follows (this is a quick and dirty example):
OpenService (hServMgr, TEXT("\\UPS_SERVICE_0"), SC_MANAGER_ALL_ACCESS);
SERVICE_STATUS stat;
ControlService (hUpsService, SERVICE_CONTROL_STOP, &stat)
Note that you need to provide a Service Manager handle in hServMgr and the \\UPS_SERVICE_0 name is the name that must match with your desired UPS service (either the Windows built-in or another).
Remember that to stop a service you need the proper security rights. This is not a problem with an Adminstration account, but keep in mind what happens when logging with a non-admin account.
Hope that helps.
About shutting down the physical UPS device, I remember back in WIn98 days I was able to poweroff the device talking with the UPS through the COM port, altough I don't remember the brand or how the programming interface was.