#FIG 2.1
80 2
2 1 0 5 -1 0 0 0 0.000 -1 1 0
	0 0 5.000 20.000 40.000
	 104 54 104 114 9999 9999
2 1 0 5 -1 0 0 0 0.000 -1 1 0
	0 0 5.000 20.000 40.000
	 269 209 269 329 9999 9999
2 1 0 5 -1 0 0 0 0.000 -1 1 0
	0 0 5.000 20.000 40.000
	 104 354 104 454 9999 9999
2 1 0 1 -1 0 0 0 0.000 -1 0 0
	 104 114 104 354 9999 9999
2 1 0 1 -1 0 0 0 0.000 -1 0 0
	 269 209 269 59 9999 9999
2 1 0 1 -1 0 0 0 0.000 -1 0 0
	 269 324 269 459 9999 9999
2 1 1 1 -1 0 0 0 4.000 -1 1 0
	0 0 1.000 4.000 8.000
	 104 109 269 149 9999 9999
2 1 1 1 -1 0 0 0 4.000 -1 1 0
	0 0 1.000 4.000 8.000
	 269 329 104 354 9999 9999
4 0 0 12 0 -1 0 0.00000 4 15 49 69 39 SENDER

4 0 0 12 0 -1 0 0.00000 4 15 61 234 39 RECEIVER

4 0 0 12 0 -1 0 0.00000 4 15 45 109 139 send and

4 0 0 12 0 -1 0 0.00000 4 15 26 109 157 block

4 0 0 12 0 -1 0 0.00000 4 15 36 284 214 receive

4 0 0 12 0 -1 0 0.00000 4 15 25 284 334 reply

4 0 0 12 0 -1 0 0.00000 4 15 38 119 364 unblock