vikonava Posting Whiz in Training

hi... i wanted to know if any of you could help me... i need to create an unidirectional link between two nodes using TCP on Network Simulator. For this, I suppose this means I need to setup a half-duplex on the tcl configuration, Ive read the entire NSnam manual and Im not able to find something that could be useful to control that. Can you help me, maybe an example or something?