Vladislav Vaintroub added a comment - 2016-03-30 17:51 - edited The actual reason why the connection is lost seems to be a bug in yassl's implementation of SSL_pending() , which is called inside vio_ssl_has_data() . The socket is doing blocking recv() inside this function, and runs into net_read_timeout after a while. After that, connection breaks. Doing blocking reads inside vio_ssl_has_data (or SSL_pending ) does not sound like a great idea. Below is the callstack of the blocking recv() calls >Debug.ListCallStack /T:No /ShowByteOffset:No /ShowValues:No /ShowExternalCode:Yes Index Function -------------------------------------------------------------------------------- 1 ntdll.dll!_ZwWaitForSingleObject@12() 2 mswsock.dll!_SockWaitForSingleObject@16() 3 mswsock.dll!_WSPRecv@36() 4 ws2_32.dll!_recv@16() *5 mysqld.exe!yaSSL::Socket::wait() 6 mysqld.exe!yaSSL::DoProcessReply(ssl) 7 mysqld.exe!yaSSL::processReply(ssl) 8 mysqld.exe!yaSSL::receiveData(ssl, data, peek) 9 mysqld.exe!yaSSL_peek(ssl, buffer, sz) 10 mysqld.exe!yaSSL_pending(ssl) 11 mysqld.exe!vio_ssl_has_data(vio) 12 mysqld.exe!threadpool_process_request(thd) 13 mysqld.exe!io_completion_callback(instance, context, overlapped, io_result, nbytes, io) --------------------------------------------------------------------------------- 1 mysqld.exe!vio_read(vio, buf, size) 2 mysqld.exe!yassl_recv(ptr, buf, len, flag) 3 mysqld.exe!yaSSL::Socket::receive(buf, sz, flags) 4 mysqld.exe!yaSSL::DoProcessReply(ssl) 5 mysqld.exe!yaSSL::processReply(ssl) 6 mysqld.exe!yaSSL::receiveData(ssl, data, peek) 7 mysqld.exe!yaSSL_peek(ssl, buffer, sz) 8 mysqld.exe!yaSSL_pending(ssl) 9 mysqld.exe!vio_ssl_has_data(vio) 10 mysqld.exe!threadpool_process_request(thd) 11 mysqld.exe!io_completion_callback(instance, context, overlapped, io_result, nbytes, io)