Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17


TCP Socket listening but does not send ACK+SYN

Posted on 2006-11-30
Medium Priority
Last Modified: 2013-11-29

I have a server that we are running several QA tests on. One test involves a java client that connects to a java server (all on the same machine). If I do a netstat , I can see that the Java server is running and listening on port 30041. When i kick off the test, I can see the client attempt a connection to the server's socket. The client socket sits there in the SYN SENT state but never appears to receive an ACK+SYN from the server socket. The client process eventually gives up and dies. Does anyone have any suggestions on how to troubleshoot this problem on a Linux box? The firewall and SELinux are turned off. What logs should I be looking at? I tried running TCPDUMP but that did not provide me with any useful info. Any help would be appreciated.
Question by:tmelo49
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 3

Accepted Solution

Trilotech earned 750 total points
ID: 18047560
Do you have multiple IP Addresses? Perhaps the client software is trying the wrong address (if you are using multiple addresses). This could mean a DNS issue if you are using hostnames.

Author Comment

ID: 18047705
Here is the tricky part that i forgot to mention, this particular server is actually a virtual OS through VMWare, but only has 1 IP and the DNS record appears fine (reverse lookup too). Even though it is a virtual OS, it functions as a completely independent OS. I really dont think the fact that it is a virtual OS is the cause of the problem. All other server/client processes talk just fine.

Expert Comment

ID: 18047809
Is it totally self contained in VMWare? Or is it an IP address that is accessible from the rest of your LAN?

If it is self contained and all other functions are working related to DNS and other networking services, then I would think the problem would be within the software. Perhaps a configuration error?

Check the documentation and perhaps contact the software developer.
Portable, direct connect server access

The ATEN CV211 connects a laptop directly to any server allowing you instant access to perform data maintenance and local operations, for quick troubleshooting, updating, service and repair.


Author Comment

ID: 18047834
It is an IP that is accessible from the rest of the network.

Author Comment

ID: 18048488
I figured out the problem......incorrect hosts file entry for localhost .

Author Comment

ID: 18048511
Thanks Trilotech. You put me on the right path.

Expert Comment

ID: 18048524
No problem. Glad you got it!

Featured Post

On Demand Webinar - Networking for the Cloud Era

This webinar discusses:
-Common barriers companies experience when moving to the cloud
-How SD-WAN changes the way we look at networks
-Best practices customers should employ moving forward with cloud migration
-What happens behind the scenes of SteelConnect’s one-click button

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

When you try to share a printer , you may receive one of the following error messages. Error message when you use the Add Printer Wizard to share a printer: Windows could not share your printer. Operation could not be completed (Error 0x000006…
This article is a collection of issues that people face from time to time and possible solutions to those issues. I hope you enjoy reading it.
Viewers will learn how to properly install and use Secure Shell (SSH) to work on projects or homework remotely. Download Secure Shell: Follow basic installation instructions: Open Secure Shell and use "Quick Connect" to enter credentials includi…
In this brief tutorial Pawel from AdRem Software explains how you can quickly find out which services are running on your network, or what are the IP addresses of servers responsible for each service. Software used is freeware NetCrunch Tools (https…

660 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question