473,803 Members | 4,391 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

How to tell if the other end of socket connection is dead without polling?

Hi,

I have a Java application which runs a server socket on a PC. Various
sensors (using microprocessors ) can call it up and each gets its own thread
running the socket connection.

The sensors send in data at random times. This all works OK.

Sometimes one of the sensors fails or goes off-line. How can I tell from
the server end? If they fail I would like to close the link down.

Obviously I could poll links on a periodic basis and mark the link as dead
after a specified timeout but this seems rather inelegant. If I chose a
short period the network might be very busy for a short time and cause a
false timeout. If the period is long then I either have to start a new
thread to handle the polling or elselive with my main application blocking.
Anyway, there might be several hundred sensors and I don't want to clutter
the network up with polling packets. Is there a better way?

I would be grateful for any help.

Regards,

Nick
Aug 25 '08 #1
2 4260
Nick Toop wrote:
Hi,

I have a Java application which runs a server socket on a PC. Various
sensors (using microprocessors ) can call it up and each gets its own thread
running the socket connection.

The sensors send in data at random times. This all works OK.

Sometimes one of the sensors fails or goes off-line. How can I tell from
the server end? If they fail I would like to close the link down.

Obviously I could poll links on a periodic basis and mark the link as dead
after a specified timeout but this seems rather inelegant. If I chose a
short period the network might be very busy for a short time and cause a
false timeout. If the period is long then I either have to start a new
thread to handle the polling or elselive with my main application blocking.
Anyway, there might be several hundred sensors and I don't want to clutter
the network up with polling packets. Is there a better way?

I would be grateful for any help.

Regards,

Nick

If you don't send data on a TCP stream, nothing is sent. There is no
detection of crashes built into the TCP protocol, so you will have to
implement this yourself.

On the client side I usually mark the time of the last packet sent and
use that for determining when a keepalive packet needs to be sent
meaning that if the application itself sends and receives data regularly
no keepalive packets needs to be sent at all. Only when the stream is
idle will I send keepalives.

On the server side I mark the time of the last received packet from each
client and have a timer to check the clients. If the server hasn't heard
from the clients in a configurable amount of time the stream is shut down.
Aug 27 '08 #2
On Wed, 27 Aug 2008 13:01:42 +0200, Robert Larsen wrote:
Nick Toop wrote:
>Hi,

I have a Java application which runs a server socket on a PC. Various
sensors (using microprocessors ) can call it up and each gets its own
thread running the socket connection.

The sensors send in data at random times. This all works OK.

Sometimes one of the sensors fails or goes off-line. How can I tell
from the server end? If they fail I would like to close the link down.

Obviously I could poll links on a periodic basis and mark the link as
dead after a specified timeout but this seems rather inelegant. If I
chose a short period the network might be very busy for a short time
and cause a false timeout. If the period is long then I either have to
start a new thread to handle the polling or elselive with my main
application blocking. Anyway, there might be several hundred sensors
and I don't want to clutter the network up with polling packets. Is
there a better way?

I would be grateful for any help.

Regards,

Nick

If you don't send data on a TCP stream, nothing is sent. There is no
detection of crashes built into the TCP protocol, so you will have to
implement this yourself.
http://www.developerweb.net/forum/showthread.php?t=2983

Sep 27 '08 #3

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

1
6139
by: Joe | last post by:
Hi, I browsed the news and a few seem to have this problem too, but no solution ! I have a client server application where in case the connection gets bad (crashes or whatever) client or server (who knows it first) closes the socket and than wants to establish the SAME connection again ( due to firewall reasons it has to be the SAME IP AND PORT).
4
3856
by: Frank Meng | last post by:
Hi. I am trying a csharp sample from http://www.codeproject.com/csharp/socketsincs.asp . (Sorry I didn't post all the source codes here, please get the codes from above link if you want to try). I had some troubles when I started 6 threads (each thread made a separate connection) and sent messages to same server simultaneously. Sometimes, not always, the socket looks like ok, but really it is dead. I don't why it happens.
7
2935
by: | last post by:
Hi all, I have a simple .aspx page running on net 2.0 that is trying to do a http post to a remote server. Here is the code Private Function ProcessRequests(ByVal strbody As String) As String Dim returnstr As String Dim URL As String = "http://www.dydomain.com/test.asp"
2
4160
by: Nuno Magalhaes | last post by:
I've got a simple problem I guess. How do I know when a connection is terminated without losing any data? I do something like the code below, but sometimes between socket.Receive and socket.Send I get the last chunk of data and am not able to retrieve it anymore cause the socket will be dead. Loop: { socket.Receive <----------- data arrives
4
1748
by: Droopy | last post by:
Hi, I wrote a program that runs on about 20 machines. Each machine is connected with a socket on all other machines. Each socket has its own handling thread. The main reading loop is using Poll () with a 100ms timeout and Receive () to check incoming data. Send () is used to send data. There are exchanging many small messages (most are less than 250 bytes). It runs well for a few hours than I got socket exceptions, mainly "An
6
2041
by: Abubakar | last post by:
Hi, lets say I have a connected SOCKET s. At some point in time, I want to know if the "s" is still valid, that it is still connected. Is there any API that I can give me this information? And can I register some callback like thing, that would inform me when "s" disconnection happens? What I usually do is while I call "send" or "recv", I get the socket_error and through that I know whats the status. But in this situation actually I...
0
4757
by: phplasma | last post by:
Hey, I am currently attempting to implement a multi-threaded C# socket, using SSL (.pem file/certification/private key combo) server using Visual Studio C# Express. I have successfully made the client application establish a connection, and send data, which appears in plain, de-crypted text on the server - this works.
11
8622
by: atlaste | last post by:
Hi, In an attempt to create a full-blown webcrawler I've found myself writing a wrapper around the Socket class in an attempt to make it completely async, supporting timeouts and some scheduling mechanisms. I use a non-blocking approach for this, using the call to 'poll' to support the async mechanism - rather than the 'begin' and 'end' functions. I already found that connecting doesn't set the "isconnected" variable correctly...
1
1295
by: jm.carp | last post by:
I'm writing a tcp client that grabs data from a server at 32hz. But the connection drops exactly one minute after it's opened. I can get data from the server fine for the first 60s, and then the connection goes dead. What's going on?
0
9562
by: Hystou | last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can effortlessly switch the default language on Windows 10 without reinstalling. I'll walk you through it. First, let's disable language synchronization. With a Microsoft account, language settings sync across devices. To prevent any complications,...
0
10542
Oralloy
by: Oralloy | last post by:
Hello folks, I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>". The problem is that using the GNU compilers, it seems that the internal comparison operator "<=>" tries to promote arguments from unsigned to signed. This is as boiled down as I can make it. Here is my compilation command: g++-12 -std=c++20 -Wnarrowing bit_field.cpp Here is the code in...
1
10289
by: Hystou | last post by:
Overview: Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows Update option using the Control Panel or Settings app; it automatically checks for updates and installs any it finds, whether you like it or not. For most users, this new feature is actually very convenient. If you want to control the update process,...
0
10068
tracyyun
by: tracyyun | last post by:
Dear forum friends, With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the choice of these technologies. I'm particularly interested in Zigbee because I've heard it does some...
0
9119
agi2029
by: agi2029 | last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own.... Now, this would greatly impact the work of software developers. The idea...
1
7600
isladogs
by: isladogs | last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules. He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms. Adolph will...
0
5625
by: adsilva | last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
2
3795
muto222
by: muto222 | last post by:
How can i add a mobile payment intergratation into php mysql website.
3
2968
bsmnconsultancy
by: bsmnconsultancy | last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating effective websites that not only look great but also perform exceptionally well. In this comprehensive...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.