This answer addresses the "initial connect" scenario for Windows 7, which is different from XP. For Windows 7, two hotfixes are required to support adjusting connect timeout settings. The new settings can be configured with the 'netsh' command. The first hotfix adds a 'MaxSynRetransmissions' setting which allows changing the retry setting from the default value of 2. The second adds 'InitialRto' setting which allows changing the Initial RTO value from the default of ms yes, milliseconds , but only to something shorter than ms; it cannot be increased.
Depending on your situation, you may only need the 'MaxSynRetransmissions' hotfix. Install both hotfixes, reboot, then open a command window as Administrator. Further reboots are not required for subsequent netsh command invocations. Note: Windows telnet is used for the reference for actual connection timeout. It needs to be installed separately, but is easy to do. This Microsoft document does not include them. During this time, reopening the connection to the client and server costs less than establishing a new connection.
You may not have it set if you are using Win or later, but the default is decimal seconds or 4 minutes that is. You can add the key to the registry with a different value and it will take effect after a reboot tested on Windows Server R2 in a production environment. This is an absurdly high value given the quality of modern networks.
I had an application literally less than a month ago running on a server that exhausted the maximum number of connections Windows can support and killed every network service on that server regularly.
We set the value to 30 decimal 30 seconds and voila, the issue was solved - less than 10, simultaneous connections since the app was rapidly opening and closing them and no throughput issues. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Ask Question. Asked 11 years, 2 months ago. The simultaneous network traces on source and destination will help you verify this behavior where on the source side you would see the packets being retransmitted and on the destination none of these packets are seen.
This would mean, the network device between the source and destination is dropping the packets. You would not see any of the above packets. Engage your network team to investigate with the different hops and see if any of them are potentially causing drops in the network. If you are seeing that the SYN packets are reaching the destination, but the destination is still not responding, then verify if the port that you are trying to connect to is in the listening state.
Netstat output will help. If the port is listening and still there is no response, then there could be a wfp drop. You see this behavior when the packets are modified in the network by middle devices and TCP on the receiving end is unable to accept the packet, such as the sequence number being modified, or packets being replayed by middle device by changing the sequence number. Again, the simultaneous network trace on the source and destination will be able to tell you if any of the TCP headers are modified.
Start by comparing the source trace and destination trace, you will be able to notice if there is a change in the packets itself or if any new packets are reaching the destination on behalf of the source. In this case, you'll again need help from the network team to identify any device that's modifying packets or replaying packets to the destination.
When you have identified that the resets are not due to retransmits or incorrect parameter or packets being modified with the help of network trace, then you have narrowed it down to application level reset.
The application resets are the ones where you see the Acknowledgment flag set to 1 along with the reset flag. This would mean that the server is acknowledging the receipt of the packet but for some reason it will not accept the connection.
This is when the application that received the packet did not like something it received. In the below screenshots, you see that the packets seen on the source and the destination are the same without any modification or any drops, but you see an explicit reset sent by the destination to the source. The application that's causing the reset identified by port numbers should be investigated to understand what is causing it to reset the connection. Hi Stephen,.
However, after a period of inactivity idle where no data passes thru the tcp connection, approx. Are you saying that the tcp connection should stay alive forever even if there are no data passing through the connection? Monday, July 20, AM.
Something else must be closing the connection. Hi Steve,. Before I start posting the lengthy code, Let me explain my situation to shed some light on the problem.
My clients are actually mobile devices, which will first connect itself to the internet via GPRS, b4 creating a TcpClient to connect to my server. At this point in time, the client will actually write some data on a network stream created from the TCP Connection to the server. My server is able to properly respond to the connection, store the tcpclient in an arraylist and read the data sent by the client.
Both are able to connect to GPRS and my server. Tuesday, July 21, AM.
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