I have created a Datasnap service, using Bob Swart's white paper as a guide. I have been debugging and deployed succesfully using the VCL Forms application as a server. But when I try to deploy the service version, it installs ok, I then try to start the service and it immediately stops. The error in the event log would suggest that the port set is already in use, I have tried different port numbers for both the TCPServerTransport and the HTTPService without any joy. The DSServer is not set to Autostart as I want to set the Port number from a configuration file. The error message displayed in the event log is:
Service failed on start: Could not bind socket. Address and port are already in use..
I have also tried writing to a log file on start up and execute but it looks as if it is not getting this far.
Solution needed asap, before I have to revert back to a thick client which I do not really want to do.
Thanks
Firstly get a copy of TCPView from the Sysinternals suite (now run by Microsoft) and use it to monitor which app is using the port you want to use.
I would hazard a guess that if the app works fine as a stand alone (as you say it does) and you are trying to use the same port in the service then perhaps the service app is opening up the port at startup without you realizing it and then when you try to open the port manually the app finds it already in use. Or somehow the app is trying to open the port twice. The first time is successful but, maybe due to an event or an unexpected code path, the app tries to open it a second time and fails. TCPView will help spot this.
If you are sure that the port you have configured is actually free and not in use by any other software on the machine, then there might be some anti-virus / security software running that is blocking all software from listening on either specific ports or on any port except a few configured ones. The message you are getting could be one of the symptoms of how the anti-virus / security software handles attempts by apps to start listening on a port.
Related
I am writing an application using Asterisk-Java. It is designed to run on a server that also runs Asterisk. So far, so good.
My application, that originates calls (using the AMI) and that manages user input (using Asterisk-Java's FastAGI and an embedded AgiServer) works great on both my development server and the production server.
For deployment purposes, I am now asked to create a Docker container that would pack up Asterisk and my application, so that it could be easily deployed to other places without having to go through installations and configurations.
The thing is, my application does not behave the same way in the Docker container: on the development / production servers, using the getData function, I can get a DTMF code; on the Docker container, getData seems to never receive the DTMF data from Asterisk (I can stream a file, but the function eventually times out, which means it did not get anything).
I first though of an unexposed port, but since this communication problem seems to be between the AGI Server and Asterisk, which are both running in the container, I find it hard to believe.
I have no other idea, please suggest.
Check out the dtmfmode Parameter for your SIP-Peer...
If your are using RFC2833 (DTMF via RTP), unexposed media ports could very well be the reason.
You could try to optimize your port settings (could be a lot of ports!).
Or try to use DMTF via SIP-Info as an alternative.
But that wouldnt fix any media problems...
I am presently working on a client-server solution to transfer files to another machine via a socket network connection. Since I intend to do some evaluation on the receiving end as well I am assuming that I will need to have some kind of client or server programme running there, too.
I am fairly new to the whole client-server thing and therefore have the following elementary question:
My present understanding is that client and server will be two independent programmes running on two different machines. How would one typically ensure that the communication partner (i.e., the server when sending from a client and the client when sending from a server) is actually up and running on the remote machine that I want to transfer a file to?
So far, I have been looking into the following options:
In the sending programme include an ssh access to the remote
machine and start an instance of the receiving programme on the
remote machine.
Have the receiving programme run as a demon process on the remote
machine. This would mean that the receiving programme should always
be running on the remote machine. However, how would I know whether
the process has crashed or has been shut down for some reason and
how would one recover from that without option 1) above?
So, my main question is: Are there any additional options that might be worth considering?
Thanks for your view on this!
Depending on how your client server messages are setup, a ping (I don't mean the ICMP ping, but the basic idea) message, where the server can respond with "I am alive" would help. This way at least you know the server end is running.
It is not uncommon in production environments using these that monitoring systems are put in place. Other options worth considering - xinet.d scripts - stuff that gets started on incoming connections.
There probably new ways to achieve the automatic start/restart or start on connection of this with systemd/systemctl but I am not familiar enough with them to give you the specifics.
A somewhat crude, but effective means may be a cron job that periodically runs a script to enforce keeping the service up.
I wrote a multi-tier application suite in Delphi XE, using DataSnap (VCL application).
This will be used internally, in my company, mostly to replace the outdated fax communication.
Everything works fine, but I came across an unpleasant situation: The server machine is behind a router, so it has an internal network IP. I forwarded (in the router) all incoming connections on port 211(DataSnap default) to the server's internal IP and about 8 times out of ten all the clients connect to the server without any problems.
The problem is that for the rest 2 times I get all sort of connection errors (mostly connection timed out). When it does this I have to close and reopen either the server application either (some of) the clients, and then it works.
Right now I'm still in the design phase, so it's only a bother, but when I do release it I don't want either to tell everyone NOT to EVER close the application (once it works, it works, no more problems), either close and reopen the applications each time there is a connection problem.
How can I eliminate this problem?
I had (only) a look at NetCat and SoCat, but (to me) it seems overkill for this situation. Is there another way to solve this?
The solution was switching off router's internal firewall.
So I have been looking every where, and so far i haven't been able to find anything that allows me to ssh from an iPhone app, and have finally resorted to posting a new pos.
So I am trying to make an app to manage servers and part of the tasks that I need to be able to do it to be able to some how remotely connect over the internet to a server with either an ip address or a DNS name.
The connection to the server does not necessarily need to be a SSH connection, it could be a telnet although because of the security issues i would prefer SSH (if it is a lot less code I would accept telnet), but on the other hand it could be some other type of connection.
The application just needs to be able to run a script on the server end and if a SSH or telnet I would not need any help but if some other type of connection i may need a bit of help. Also the server on the other end is intended to be linux server (either ubuntu or gentoo, but not sure which yet but all i can say is will almost certainly be a linux server operating system).
I have already looked at the libssh/2 and would welcome any other similar demos as have not been able to work out how get the frameworks to work as well as licensing issues with using the frameworks in it.
PS. I am relatively new to programming and although i have some basic knowledge of coding some type of tutorial or sample code would be greatly appreciated.
Many Thanks For Any Help
Thomas
SSH is a hugely complicated beast. As long as you only need to execute one command without interactivity, it sounds like you could achieve the same thing by running a web server on the server and posting the commands via HTTP from the device. You can use SSL to achieve security. You'll need a mechanism that allows you to authenticate the device (you'd need something with ssh, too). And you'll have to have something in the web server on the server that figures out and runs the desired script. But all that is still hugely easier than dealing with libssh.
I built an application that is running as a windows service and is installed through my code.
All is fine except at logon.
When at the first windows xp/2003 server logon screen, I am not sure if the service is running at all. If it is, then it does work as it's not functional (the service IS USING WINPCAP so that could be an issue).
The service settings are set to "interact with desktop" and run as SYSTEM.
How can I ensure the service will start before windows logon? Also how can I make sure it is running even after I log off?
There are a couple of issues to consider.
First, you can check if your service really is running before login and after logout by logging events to the Windows Event Log. Pretty much all services do this whenever they start and stop and yours should do the same.
It may be that WinPcap is part of the problem. There are a couple of golden rules for using WinPcap in a service.
1a) Your service must not do anything that might cause the WinPcap service to try to start up while your own service is starting up because this will cause a deadlock in the Windows Service Control Manager. That means that if the WinPcap service is not already SERVICE_RUNNING when your service begins startup, you must not do anything that might cause it to start until after your service is SERVICE_RUNNING.
There are two ways to ensure this. Either make your service dependent on npf, the Network Packet Filter service. Or do not call any WinPcap function until after your service is SERVICE_RUNNING. I've not tried this latter method. I presume then the WinPcap function will block until npf is SERVICE_RUNNING.
1b) If you make your service dependent on npf, you will also have to make it dependent on nm (Network Monitor Driver) - if and only if nm is installed on the system. nm provides WinPcap with PPP/VPN support, and WinPcap always tries to use it if installed. Obviously, if you make nm a dependency of your service and nm isn't installed then your service will fail to start.
I don't think there is a guaranteed way to ensure that your service starts up before the desktop appears. But you might be able to help things along by creating a Service Control Group, adding it to the end of the existing list of Service Control Groups, and putting your service into this group. I'm not entirely convinced that this is an 'approved' way to get your service to start sooner, because if there was an approved way then everyone would do it and it wouldn't work any more. But there is a suggestion that services in a group are started before services not in a group.
Look at HKEY_LOCAL_MACHINE, "SYSTEM\CurrentControlSet\Control\GroupOrderList" and HKEY_LOCAL_MACHINE, "SYSTEM\CurrentControlSet\Control\ServiceGroupOrder" and do a bit of Googling.