I am using strophe.js to intract with xmpp . it has the feature to restore its states when network fluctuate. this work okay for short time but when network got connected after 5 to 10 min fater disconnection it didnt restore its connection. any ideas why this it is so?
You can use connection manager for this. see this one
Basically what you to do is that start a timer when network get disconnected and in that timer check network connection. once network found connected relogin the strophe to make it working.
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I installed postgreSQL server on a raspberry pi 4 with raspbian buster. When I try to connect from local network i have no problems about idle time. When i try to connect from my static public ip I can send command but if I didn't send anything for more than 3 minutes, it appears this message "Connection to the server has been lost".
I tried to install ufw and disable it, I used DMZ, I tried to change keepalive_idle, but i have always the same problem. Please help me.
sometimes the error is
"ERROR: SSL SYSCALL error: Operation timed out"
(Note: always if I am connected from public IP)
If you don't have the same issue from within your local network I assume the connection is being terminated by a network device sitting between the client and the server (a router most likely).
There are routers with small TCP timeout settings (such as 300 seconds) which is close to what you're experiencing.
Try to check (and increase if needed) the TCP timeout settings on your router (and any other devices you might have in between).
Edit:
I tried to find some info on that device (seems to be Sercomm VD625) and it does not seem you can easily change TCP timeout settings (maybe via telnet/ssh if it supports it).
However, a simpler solution might be to avoid keeping an open connection to PostgreSQL if you will have large idle intervals; just connect when you need to and close the connection afterwards.
I am using the wifi chip ESP8266 with SMING framework.
I am able to establish a TCP connection as a client to a remote server. The code for initiating client connection to server is simple.
tcpClient.connect(SERVER_HOST, SERVER_PORT);
Unfortunately, the connection will close after idling for some time. I would like to keep this connection open forever permanently. How can this be done?
You will actually need to monitor the connection state and reconnect it if it failed. Your protocol on top of it will need to keep track of what got actually received by the other side and retransmit it.
In any wireless network your link may go down for one reason or another and if you need to maintain a long term connection you will need to have it in a layer above TCP itself.
TCP will continue to be connected as long as both sides allow for it (none of them disconnected) and there are no errors on the link, in this case sending keepalives may actually cause disconnects since the keepalive may fail at one time but the link could recover and if you didn't have the keepalive the link would have stayed up.
The situation:
Postgres 9.1 on Debian Server
Scala(Java) application using the LISTEN/NOTIFY mechanism to get notified through JDBC
As there can be very long pauses (multipla days) between notifications I ran into the problem that the underlying TCP connection silently got terminated after some time and my application stopped to receive the notifications.
When googeling for a solution I found that there is a parameter tcpKeepAlive that you can set on the connection. So I set it to true and was happy. Until the next day I saw that again my connection was dead.
As I had been suspicious there was a wireshark capture running in parallel which now turns out to be very usefull. Just about exactly two hours after the last successfull communication on the connection of interest my application sends a keepalive packet to the database server. However the server responds with RST as it seems it has already closed the connection.
The net.ipv4.tcp_keepalive_time on the server is set to 7200 which is 2 hours.
Do I need to somehow enable keepalive on the server or increase the keepalive_time?
Is this the way to go about keeping my application connected?
TL;DR: My database connection gets terminated after long inactivity. Setting tcpKeepAlive didnt fix it as server responds with RST. What to do?
As Craig suggested in the comments the problem was very likely related to some piece of network hardware in between the server and the application. The fix was to increase the frequency of the keepalive messages.
In my case the OS was Windows where you have to create a Registry key with the idle time in milliseconds after which the message should be sent. Info on that here
I have set it to 15 minutes which seems to have solved the issue.
UPDATE:
It only seemed like it solved the issue. After about two days of program run time my connection was gone again. I switched to checking the validity my connection every time I use it. This does not seem like it is the solution but it is a solution nonetheless.
Sessions are getting disconnected automatically (in the middle of working).
Disconnection happens for the users when they working by using telnet connection to Linux server via putty telnet application.
During the disconnection, the Network b/w utilization is high and no limitation for total number of users in a network.
Error "Hangup signal received (562)"
Any idea about this ??
The network connection was interrupted or a hangup signal was sent via "kill".
You mention network utilization being "high" when disconnects happen. How do you know that? What measurement are you looking at that tells you it is "high"? That might be a symptom of a networking issue that is at the root of the problem.
There are few directions:
OpenEdge has published this article with links to implementing keep-alive packets:
https://knowledgebase.progress.com/articles/Article/Telnet-connection-times-out-after-15-minutes
Increase the number of "instances" in xinetd.conf, and then restart the service.
Make sure that the database watchdog is up and running: https://documentation.progress.com/output/ua/OpenEdge_latest/index.html#page/dmadm/prowdog-command.html
Check the database log file, to find out what happened just before the hangup (https://documentation.progress.com/output/ua/OpenEdge_latest/index.html#page/gsins/openedge-database-log-file.html)
I use AsyncSocket to establish tcp connection via Wifi to a server, and after 10 seconds, the server will actively close the connection.
When the iPhone is not in standby mode, the connection will be destroyed immediately after the server call ::close(int socked).
But when the iPhone is in standby mode, I find the connection is still alive when the server has called the ::close(int socketfd) API.
Can anyone give an explanation?
The Problem is that your server send the close question and wait for a answer of the client that it even will close the connection. Your IPhone is in Standby and can't send any question or answers, if the connection is dead it should be auto close, maybe you have to implement a connection dead function for this case.