Hello. I am experiencing some very strange symptoms with some programs that communicate using ICS.
Summary: The programs communicate fine (stable and consistent) when they are run on DIFFERENT machines. However, when run on the SAME machine, the communication between the programs is very unpredictable (sporadic failures, varying in frequency). In contrast to this, there are CERTAIN machines, where they DO run fine (stable and consistent) on the same machine. Oddly the working machines have Delphi installed on them and the failing machines do NOT have Delphi installed on them (which shouldn't matter). Detail: (sorry so long) I have implemented a thin client architecture using a basic Server / Client pattern. Meaning, there are two programs; one functions as a Server (actually a Broker) using TWSocketServer and another Client program uses TWSocket. The Client program initiates the connection and generates TCP traffic of a varying nature, depending upon specific user activities. The sessions are persistent (the client stays connected for the life of the application). The session traffic uses my own packetized protocol, something I have done many times (including with ICS). The Server uses a single TWSocketServer on the Main Form for all communications, meaning no Server based threads for TCP handling. However, while processing inbound packets from the Client program, it does hand some chores off to a thread pool that does the mundane chores (DB lookups, etc). A thread may or may not send one or more packets to the client, depending upon the particular protocol chore they were handling (requesting data of different types, reporting on Client interface activities, etc). The Server's outbound packet calls via the TWSocketClients all funnel through one critical section, which should provide thread safety for outbound traffic. There are a few other items that may worth noting. There is an additional load balancing program (Router) that is not directly engaged in the session. The Client first connects to the Router, which provides Server connection information to the Client. The Client disconnects from the Router and re-connects to the directed Server. There is an Admin channel between the Router and Server (Broker) that provides intelligent load balancing info, which OBVIOUSLY uses a SEPARATE socket interface, distinct from Client / Server channel. Additionally, this all occurs on top of my own Secure Channel implementation, which uses bi-directional BlowFish encryptors and multiple private keys to seed various encryption and randomizing algorithms. Also, I am using a MySQL Database via the MicroOLAP MySQLDAC components, which MicroOLAP claims is thread safe and appears generally to be. Oddly, the Client and Server programs work fine when both are running on my 2 development machines. (As a result, I didn't catch this issue until later in development, like before a demo. :-( ). However, when I try to run both of them on any other machine (so far), they communicate very poorly. Basically, they experience symptoms of random packet drops, but I don't think that is actually the case. I can't really tell, because I can not reproduce the scenario on a development machine where I could trace and debug the issue. The session will just hang, usually during the handshaking stage (Channel setup), but not always. However, if the Server and Client are on DIFFERENT machines, they work wonderfully, no problems at all, no matter what MACHINES they are on. I have tried a BUNCH of things to attempt to isolate and / or alleviate the problem. I have changed the Threading property on the Server Socket, which seems to have no effect. I have also tried using local MySQL Server vs. Remote MySQL server, no effect either way. As well as a many other tests / solutions. All to no avail. I am stumped in a big way. I understand that this is a really complicated implementation and my issue could be caused by a NUMBER of things. However, most of my testing seems to isolate the issue to the communications layer, for some unknown reason. I have never seen a scenario where the programs run fine from different machines, but won't work on the same machine. I am really hoping someone might have seen something similar? Could it be a WinSock bug? Any help would be appreciated. Thanks much. Hoby -- To unsubscribe or change your settings for TWSocket mailing list please goto http://www.elists.org/mailman/listinfo/twsocket Visit our website at http://www.overbyte.be
