Hello, I have a problem to estabilish HTTPS connection with another server. When I check the communication in Network monitor, I see only single frame outgoing from my server to destination server. The description of the frame is: TLS: TLS Rec Layer-1 HandShake: Client Hello. No other frame is ever send or received in this communication = Server Hello never arrives. The complete story: I am developer and I have only very little experience with diagnostics of such problems. Also my knowledge of protocols is very limited. I'm deploying application which calls web services hosted on a server running SUN Solaris. HTTPS is required to call these services. The application is written in .NET Framework 3.5 SP1 and uses WCF to communicate with services. Everything worked well on testing and acceptance environment but on the production environment the above described issue occured. Other related informations are: Running Windows Server 2008 Standard Edition Current application is testing console application (tryed to run with elevated privileges with same result). Real application will be hosted in IIS Application (WCF) error is: An error occured while making the HTTP request to ... This should be due to the fact that the server certificate is not configured properly with HTTP.SYS in the HTTPS case. This could also be caused by mismatch of the security binding between the client and the server. Application (WCF) internal error is: Authentication failed because the remote party has closed the transport stream. Event log (Windows log) does not contain any related information, warning or error. Certificate should be correct. As I understand it we are using certificate of trusted root authority and service certificate is negotiated during TLS handshake. Called services are not exposed on default port (443) but on 2493 HTTP proxy is not used Ping to IP address and name works Nslookup for translating name to ip works Telnet to destination server and port works TLS connection to other server (Windows server hosting SQL server) works Most interesting: Access to a web page hosted in the same web site as services (=same host and port) works from IE (and no certificate error occures). But network monitor shows different sequence. It doesn't use TLS but SSL directly. When accessing from my application, destination server's http log does not show any incomming connection. When accessing from IE it does. Local firewall and antivirus are turned off at the moment Again everything works in other environments, the only things I changed when moving to production environment was destination URL and certificate. Do you thing that this is application related error, system configuration related error or network related error? I'm lost at the moment so any idea or help would be awesome. Thanks in advance, Ladislav