Push design

Everything in the communication has time limit

In push design, one of the bigger challenge is to make sure that both server and client side are storing the data/request into a "queue" and then to be handle when some threads are free to process the data/request. By using the "queue", the client/server can end the current method call after the data/request has been queued for later processing.

In the WCF context, you have two types of design to process the data/request:

1. using "function" design (works like "DateTime.Now" which returns the value immediately) - for example, the client sends "current time" command to the server and expecting the server responding (almost) immediately at the end of the calls.

2. using "callback" design - for example, the client sends "current time" command to the server and does not wait for the server respond. Instead, the server will send the current time through callback.

Both designs have pros and cons and it all depends on your need.

- The "callback" design allows the server to take it's precious time to prepare the necessary data for the client. In case the server is busy or the resources were blocked, it just have to wait until those resources were freed up. It also allows the server to schedule the process later. Upon completion, the server will make callback to the client. This is acceptable if it is not a real-time system.

- The "function" design - the client is always waiting for the result and it needs it now. By using this design, your server is running on deadlock risk (i.e., competing for the resources and locked the resource that other client is asking for). Since all the clients want it now, the deadlock will occur as soon as the same resources were requested by multiple clients. Of course, the deadlock can be avoided with proper locking mechanism.

Even with WCF, the connection will get disconnected

This is not true if you have full control over the server and client. WCF allows the system administrator to tune the "keep alive" time limit. Just in case you don't have the full server access, you need to do something to keep the connection alive.


This can be done by sending NOOP command (i.e., a dummy command that does not perform any action) from client to the server - this will keep the connection alive. In case the connection has broken, you just need to re-establish it.

To send the NOOP command repeatedly, you just need a System.Threading.Timer object which queuing the NOOP command in every 1 or 2 seconds.