On a Debian machine I'm using an OPCUA server https://github.com/FreeOpcUa/opcua-asyncio. The server does not give the possibility to enable TCP keepalive on the port opened by the server.
Basically, I want to know if it's possible to start the server then in another script, enable the tcp keepalive on that port.
I also found some other information from Redhat https://access.redhat.com/solutions/19029, and https://access.redhat.com/solutions/25773 (requires you to sign up to see the articles). But again I'm still lost as to what to do exactly.
I'll keep reading up on this, but so far I've spent about 10 hours trying to figure out whether it's even possible. So I thought I should ask for some help.
Any advice is welcome, thanks!
For operations of socket of another process socket must be shared from it https://docs.python.org/3/library/socket.html#socket.socket.share or duplicated.
Its easier to patch your server for keepalive.
Related
I don't have any code yet, so please feel free to move this to a sister site, if you think it belongs there :)
I have a Program A ( I don't have it's source code, so I can't modify it's behavior ) running on my machine which keeps listening to a particular port on the system for TCP data. It's a Peer to Peer application.
System 1 running A ====================== System 2 sunning A
The program A is supposed to run on systems where I may not be allowed to modify Firewall settings to allow incoming connections on the port the program listens to. I have an EC2 linux server running Ubuntu 16.
So I thought I can use an existing tool or create a program that would connect to the server on port X, and fetch the data from the server, and locally throw that data to the port A is listening to.
System 1 running A ========= SERVER =========== System 2 sunning A
What kind of configuration should I have on the server ? And is there any program I can use for this, or an idea of how to make one ?
I did something similar to bypass firewalls and hotspots.
Check this out https://github.com/yarrick/iodine, with a proper configuration your would be able to send\receive packets as DNS queries which is I know is always allowed, I used my server to get usual internet access with any hotspot I found.
You would lose some time, higher latency but you will have access.
Hope I helped.
I am trying to find somw Windows based tools that can help me validate TCP and UDP connection on remote machines.
My Problem (just one use case):
At work, I manage many clustered servers that I run load tests against. In order to get a rich test, I use Jmeter-Plugins which provides a Server agent that opens a TCP socket on port 4444 on a target remote machine: http://code.google.com/p/jmeter-plugins/wiki/PerfMonAgent
There are many times when I setup a new load test farm, that either the network, or the server configuration, or the ServerAgent itself can have issues and thus not allowing a Load test client to access that TCP connection.
The issue I have is that I dont know what part of the system is broken.
What I think I need:
I would like to know how I can open a TCP (not HTTP with cUrl), connection to a remote server to validate that the network allows the connection, as well as the Server firewall allows the given TCP connection to be accessed remotely.
What I have looked:
These are some of the tools I have looked at so far:
Nmap http://nmap.org
Ncat http://sourceforge.net/projects/nmap-ncat/
TCP/IP Builder http://www.drk.com.ar
Zenmap 6.01 and nmap might do the job I want, but some machines where not accessible to Zenmap when I know 100% that the server was accessible via HTTP, so that was strange.
I have looked at many tools and either they:
Dont allow remote connections
Dont seem to want to connect to a TCP socket
Or I dont understand the tools to accomplish the validation I stated above.
I would greatly appreciate all comment and suggestions to help with this re-occurring problem I face.
Mick,
Firebind.com can do what you'd like to do. Firebind is an Internet based server that can listen on any of the 65535 UDP or TCP ports. It uses a java based client to send traffic to and from the server from your machine.
Carl
www.firebind.com
I'm using beanstalkd to offload some work to other machines. The setup is a bit unusual, the server is on the internet (public ip) but the consumers are behind adsl lines on some peoples homes. So there is a linux server as client going out through a dynamic ip and connecting to the server to get a job. It's all PHP and I'm using pheanstalk library.
Everything runs smoothly for some time, but then the adsl changes the IP (every 24h hours the provider forces a disconnect-reconnect) the client just hangs, never to go out of "reserve".
I thought that putting a timeout on the reserve would help it, but it didn't. As it seems, the client issues a command and blocks, it never checks the timeout. It just issues a reserve-with-timeout (instead of a simple reserve) and it is the servers responsibility to return a TIME_OUT as the timeout occurs. The problem is, the connection is broken (but the TCP/IP doesn't know about that yet until any of the sides try to talk to the other side) and if the client blocked reading, it will never return.
The library seems to have support for some kind of timeouts locally (for example when trying to connect to server), but it does not seem to contemplate this scenario.
How could I detect the stale connection and force a reconnect? Is there some kind of keepalive on the protocol (and on the pheanstalk itself)?
Thanks!
You could try to close each connection right after the request is answered and reopen a new connection each time.
There is no close() function but you deleting the Pheanstaly Object with unset($pheanstalk) will close it.
This explanation is quite helpful:
Pheanstalk (PHP client for beanstalk) - how do connections work?
I haven't tried it yet, but I came up with the idea of connecting to the beanstalk server through an SSH tunnel. We can enable the ServerAliveCountMax and ServerAliveInterval options on the tunnel, so that a network or server failure will cause the tunnel to close. This should then cause the pheanstalk client to report an error.
stupid problem. I get those from a client connecting to a server. Sadly, the setup is complicated making debugging complex - and we run out of options.
The environment:
*Client/Server system, both running on the same machine. The client is actually a service doing some database manipulation at specific times.
* The cnonection comes from C# going through OleDb to an EasySoft JDBC driver to a custom written JDBC server that then hosts logic in C++. Yeah, compelx - but the third party supplier decided to expose the extension mechanisms for their server through a JDBC interface. Not a lot can be done here ;)
The Symptom:
At (ir)regular intervals we get a "Address already in use: connect" told from the JDBC driver. They seem to come from one particular service we run.
Now, I did read all the stuff about port exhaustion. This is why we have a little tool running now that counts ports and their states every minute. Last time this happened, we had an astonishing 370 ports in use, with the count rising to about 900 AFTER the error. We aleady patched the registry (it is a windows machine) to allow more than the 5000 client ports standard, but even then, we are far far from that limit to start with.
Which is why I am asking here. Ayneone an ide what ELSE could cause this?
It is a Windows 2003 Server machine, 64 bit. The only other thing I can see that may cause it (but this functionality is supposedly disabled) is Symantec Endpoint Protection that is installed on the server - and being capable of actinc as a firewall, it could possibly intercept network traffic. I dont want to open a can of worms by pointing to Symantec prematurely (if pointing to Symantec can ever be seen as such). So, anyone an idea what else may be the cause?
Thanks
"Address already in use", aka WSAEADDRINUSE (10048), means that when the client socket prepared to connect to the server socket, it first tried to bind itself to a specific local IP/Port pair that was already in use by another socket, either an active one or one that has been closed but is still in the FD_WAIT state. This has nothing to do with the number of ports that are available.
I'm having the same issue on a Windows 2000 Server with a .Net application connecting to a SQL Server 7.0. There's like 10 servers with the same configuration and only one is showing this error several times a day. With a small test program I'm able to reproduce the error by just establishing a TCP connection on the SQL Server listening port. Running CurrPorts (http://www.nirsoft.net/utils/cports.html) shows there's still plenty of available ports in range 1024-5000.
I'm out of ideas and would like to know if you've found a solution since you've posted your question.
Edit : I finally found the solution : a worm was present on the server (WORM_DOWNAD.A) and exhausted local ports without being noticed.
I'm trying to see the results of an incoming ping on a target windows machine. This is needed to verify that the ping, which is running in a background thread, is being sent from the originator.
I have tried netstat to no avail. Are there any other approaches I could try?
Thanks.
Ping is an ICMP packet and doesn't create a TCP connection (hence you won't see it in netstat). On Linux, I'd add a rule to the firewall.
The most simple solution for your case might be to open a connection and close it. That will add it to the output of netstat with WAIT_CLOSE.
As Aaron Digulla already noted, ping is ICMP. This also means the originator even less trustable then with TCP; there's no SYN/ACK handshake. You just get an IP packet on your host, and you have to trust the header fields. Anyone can spoof those header fields, with almost no restrictions (It might be a bit challenging to get an IP claiming to come from 127.0.0.1 past a router)
Therefore, ICMP is not suitabel for verification tasks. You need a challenge/response protocol. TCP works reasoanbly well as long as you can trust the network but not necessarily all hosts on it (a reasonable assumption for the Internet. Not strong enough for financial transactions, which is why they use SSL)