For the below symptoms, I would recommend a watching the application port with WireShark.
This should show any the TLS protocol deviations and any problems in handling and establishing the TCP connections. On 2021-08-19 00:38, David Bowers via openssl-users wrote:
* We have a server that has around 2025 clients connected at any instant. * Our application creates a Server /Listener socket that then is converted into a Secure socket using OpenSSL library. This is compiled and built in a Windows x64 environment. We also built the OpenSSL for the Windows. The Listener socket is created with a default backlog of 500. The Accept socket is non-blocking socket and waits for connections * Every Client makes a regular blocking connection to the Server. The Server accepts the connection after which the Client socket is converted to a secure socket using the OpenSSL Library. * The connections are coming at a rate of about 10 connections /second ? Not sure about this number. * We are able to connect to all the clients in a few minutes and it stays like that for some time. There constant exchange of messages between Server(COS) and clients without issues. * The application logic is to keep trying to connect every timeout. * After maybe a few hours/days we see the clients dropping connections. The logs indicate the SSL_Read or SSL_Write on the Server fails for a client with SSL_Error number 5 (SSL_ERROR_SYSCALL) and the equivalent Windows error of WSATimeOut. We then observe the WSAECONNRESET as the Client closed connection. We see this behavior for multiple sites. * The number of Clients disconnected starts increasing and we see the logs in the Client where the server refuses any more connections form Clients (10061- WSAECONNREFUSED) There is nothing to indicate this state in the server logs. Our theory is the backlog is filled and Server refusing further connections. * We are trying to find why we get the SSL_Read/SSL_Write Error as it a Blocking socket. We cannot use to a non-blocking socket due to platform and application limitation
Enjoy Jakob -- Jakob Bohm, CIO, Partner, WiseMo A/S. https://www.wisemo.com Transformervej 29, 2860 Søborg, Denmark. Direct +45 31 13 16 10 This public discussion message is non-binding and may contain errors. WiseMo - Remote Service Management for PCs, Phones and Embedded