@jsulm

Here is Reproducible Example

#include <QApplication> #include <QSslServer> #include <QDialog> #include <QSslKey> #include <QMessageBox> int main(int argc, char **argv) { // create an Application QApplication app(argc, argv); // set the ssl configuration auto config = QSslConfiguration(); // set certificate config.setLocalCertificate(QSslCertificate::fromData(QByteArray::fromStdString(R"( -----BEGIN CERTIFICATE----- MIIDITCCAgmgAwIBAgIVAMdt4c6oGd0rUSbR+/tBVfhny3K3MA0GCSqGSIb3DQEB BQUAMEoxGDAWBgNVBAMMD0xBUFRPUC1KQzJNMzcyQTEbMBkGA1UECgwSc3JpbGFr c2htaWthbnRoYW5wMREwDwYDVQQLDAhjbGlwYmlyZDAeFw0yMzA5MDgxMTQ4NDZa Fw0yNDA5MDcxMTQ4NDZaMEoxGDAWBgNVBAMMD0xBUFRPUC1KQzJNMzcyQTEbMBkG A1UECgwSc3JpbGFrc2htaWthbnRoYW5wMREwDwYDVQQLDAhjbGlwYmlyZDCCASIw DQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBALkFDUKmzz+NE0x7o5JGgE8KZ/cB GEtTwN2cElMESQ/MZe3ohIE5GdFkld/7894wXZAJkXu38oZVEQ/AurntqqSHT4iP 7qMUJGYjo2v2g/1JwU3E/sG+IjatOjyl8b0b+E9TmDt7XOS4VWz3vjTkXwmQTzUv 3L5myfdcmBpA9AOXxH8yHq9lcBl97ZHGWA4zI9uWnwtyFWSl8DX4H/y14+itEYwH n6xLsEBxqjx40G7WR0AiAYRdE5Yvr6QOGtFAeODFqOv/2sAxdm/7P1wHjIvyOB++ eufvPyWZpzeBfEvrIeGkj91YGAV7FQsOfCuzetGgZcLiBDAZKjnKEQ2oajUCAwEA ATANBgkqhkiG9w0BAQUFAAOCAQEAD/SYccAb3K6GKyfc9Rbaj44IxpsNlHDQAr5b c8Nmz+LW905EqFe6tAhCgi3q9o3HUUeiNHe0rYad3Lgd1setSOVdWiSbxArmELgW Dg3NGd3GIIRShvmZfSHRkpvKaD9j06CVzMrM0nZsjQVcQrKlFBUJ9UEqVmmcz1nU a4yUEQ9Rb7t4Icw7aD07NqLRlhNGCii4d12NAY7kRZdLdtTw7T/j4tXxmcJsOiWK Lx/cqqTBgBHc3l3EeylQdO17pFClY5yMUGGla7LPcDm1sU4mmFEKmkjcRGu+mQM2 V3EDgh37GyTWvs6Zf86B14m/US0Ff4vQu26vco5Pjk3xKckA+Q== -----END CERTIFICATE----- )")).first()); // set private key config.setPrivateKey(QSslKey(QByteArray::fromStdString(R"( -----BEGIN RSA PRIVATE KEY----- MIIEpAIBAAKCAQEAuQUNQqbPP40TTHujkkaATwpn9wEYS1PA3ZwSUwRJD8xl7eiE gTkZ0WSV3/vz3jBdkAmRe7fyhlURD8C6ue2qpIdPiI/uoxQkZiOja/aD/UnBTcT+ wb4iNq06PKXxvRv4T1OYO3tc5LhVbPe+NORfCZBPNS/cvmbJ91yYGkD0A5fEfzIe r2VwGX3tkcZYDjMj25afC3IVZKXwNfgf/LXj6K0RjAefrEuwQHGqPHjQbtZHQCIB hF0Tli+vpA4a0UB44MWo6//awDF2b/s/XAeMi/I4H7565+8/JZmnN4F8S+sh4aSP 3VgYBXsVCw58K7N60aBlwuIEMBkqOcoRDahqNQIDAQABAoIBADf6I0zrEwDzOceG ELMMyX0gdNvyZNtFd7CUq6aaQVCaUqxsEMrX78u+VunxXJL4pxYRDwcTXDjwO708 XkIqedpVZea3RUfprCmK1sKvTrevPOC+nSUY1Vkdh+UZf83rTHETpZc5d51rd80E F3QBNA+8rXo2BN9GUgyY4xvuUuVS3drVZ6WA9A9yPtaBgeLATqmb0Ckh2aVn+XG9 eYIxiF0Sfnb3HET7IDO+Xtw8OIygq+dT9v5LMMYf/Aa8aakJMoTK6SLbjFWs5gUj mhBSBdxqdmLLTa2E+3hrZOfgQ0tk85336n7v3dFKkhTMr9KztOIh53Ruh36gR3UT QxbCyvECgYEA2uKcFmrkGa61WarqSbB58e/m111cmlcjOSoEELwb+O1pLe8qqDSZ UeLVMRW+omdyvt0N1RaDEOsBWtgup2RntutEx8sAi5O1d+CrCLZ7xZJPSrYH4tIs YFXoBgCNqn+275ZdeL5LgxuFKAstFW9YbWpsXCEPbrIMBk4Xm3m3Pt8CgYEA2GRo I+lLPvcslTwens+5sXT5+EPTcY9Ss2jSz3njEIt4asxa/P4H7Xx2EWqMQg5LGSVD MP8L9lxCSiyYvrQhYAQZq2VqvVCejFkrWY8hntDvyhJ26SfanSdMB1MVWOc16dns wjuuX3+5QIQoMogL1eng6/VOOJHVfiAh57yqPWsCgYEAkcI54wvHXfrjtRSF9BBb BGuXM29ujTDdueFq16IMlpWyZu5PX7e3Kbp98bPjQM7WsJcP8QiOuyNjwZUYbEwG bN767HkYodn5DB1GiATNI2Is/zl8wuTmvDg4zFZuAE4QCjf9grxmGKao42Od4BpH roUiJ6+0USirrT8vpU9GYc0CgYAYuIfJKnrFK7m1JtQcsoB1THbOLPl37La29k+3 EialmjlcghIW+vJu6BwY60Iwva9IpSAi9dApCesszCF7D9sMPAuur/xculwSjpFM PvTJTvdF74wUINBxya5+27gBmxBmsdXBbs4B7PZ971skQrSPcJOYgUK5ZbetHACj l8MfFwKBgQC3g39rKU/iahrr5VcbLecsdv9jhSo+PANQOXhreEZTOF1spsWh9bMN 11MB0uZu99p4Solvv0M11Md++CO3ocBRT0AsdsdLdytAb+YWM+c1ls5dhjVnaMpL dKKHiQ7sfiPM05f6HuTmMuinSLw7f1Ff7GVJUMugJCqiNn3XO3jWGQ== -----END RSA PRIVATE KEY----- )"), QSsl::KeyAlgorithm::Rsa)); // peer verify config.setPeerVerifyMode(QSslSocket::VerifyPeer); // if any of them is null if (config.isNull() || config.localCertificate().isNull() || config.privateKey().isNull()) { throw std::runtime_error("Can't Create QSslConfiguration"); } const auto processSslErrors = [=] (QSslSocket * sock, const QList<QSslError> & errors){ // create a dialog auto dialog = QMessageBox(QMessageBox::Critical, "SSL Error", "Accept ?", QMessageBox::Yes | QMessageBox::Cancel); // show the dialog dialog.exec(); // if user accepted if (dialog.result() == QMessageBox::Yes) { sock->ignoreSslErrors(); } }; // create the server auto server = new QSslServer(); // set the ssl errors handler QObject::connect(server, &QSslServer::sslErrors, processSslErrors); // set the ssl configuration server->setSslConfiguration(config); // listen to the port server->listen(QHostAddress::Any, 7000); // exec return app.exec(); }

In Client Side:

openssl s_client -connect 127.0.0.1:7000

You can see the client disconnected while the dialog is in open

It's because Qt (or rather QSslSocket) closes the connection immediately after emitting the error() signal.