code: the sender and receiver call sequence

Take TCP call sequence as example:

receiver:
----------------------------
main():
	run_ntttcp_receiver():
	|-----> pthread_create() to create test threads and each thread does:
	|		|-> run_ntttcp_receiver_tcp_stream():
	|			|-> ntttcp_server_listen()
	|			|-> ntttcp_server_epoll(), or ntttcp_server_select()
	|				|-> if (no_synch), then: turn_on_light() once any data received
	|-----> if (!no_synch), then: pthread_create() to create sync thread create_receiver_sync_socket():
	|		|-> reply sender sync requests
	|       |-> turn_on_light() once sender requested
	|-----> while (1), do:
			|-> wait_light_on()
			|-> reset perf counters
			|-> run_test_timer()
			|-> wait_light_off()
			|-> turn_off_light() will be triggered by:
			|	|-> test timer expired, or 
			|	|-> Ctrl+C signal captured
			|-> calculate receiver side perf stats
			
			
sender:
----------------------------
main():
	run_ntttcp_sender():
	|-----> if (!no_synch), then: create_sender_sync_socket(): 
	|		|-> query_receiver_busy_state()
	|		|-> negotiate_test_duration()
	|-----> pthread_create() to create test threads and each thread does:
	|		|-> run_ntttcp_sender_tcp_stream():
	|			|-> create socket and connect to TCP server
	|			|-> wait_light_on()
	|			|-> do test (call n_write()) while (is_light_turned_on())
	|-----> if (!no_synch), then: 
	|		|-> request_to_start()
	|-----> turn_on_light()
	|-----> run_test_timer()
	|-----> wait_light_off()
	|-----> turn_off_light() will be triggered by:
	|		|-> test timer expired, or 
	|		|-> Ctrl+C signal captured
	|-----> pthread_join() to wait all threads exit after light is off
	|-----> calculate sender side perf stats