Calling nodes from .net with parameters

Can .net call the nodes? Can we pass parameters from .net to nodes? If yes, how?

As I know you cannot call nodes even from Java, but you can execute workflows in batch mode. I guess it is possible with (as it can run eclipse), but I have dubts about the usefulness of running eclipse with a .NET JRE if you cannot interact with it. In guess the best choice is executing the workflow in batch mode as a separate process (with a normal, native JRE).

Can Knime run as a service and accept TCP/UDP messages?

Simple answer: No. The only way to integrate KNIME into other applications is either inside another Eclipse application or by using the Batch Executor.