Parallel Start incompatible with SocketCommandProcessor

[pharrishur]

Specifying parallel start of threads along with a SocketCommandProcessor results in a java.lang.NullPointerException. The following command attempts to start threads in batches of 4 (-wp true -wc 4) and uses the SocketCommandProcessor

java -Xms768M -Xmx768M -Xmn600M JMSPerfHarness -su -wt 10 -wi 0 -nt 280 -ss 5 -sc BasicStats -rl 0 -id 5 -tc jms.r11.Sender -d REQUEST -to 20 -db 1 -dx 1 -dn 1 -jb *UC01QM -jt mqc -pc WebSphereMQ -ms 2048 -rt 1 -ccdt ccdt.json -ar WMQ_CLIENT_RECONNECT -an mqperf.receiver -cmd_c SocketCommandProcessor -wp true -wc 4

After the 280 threads are started a null pointer exception is thrown by the SocketCommandProcessor (starting threads singly works ok)

...
Sender279: START                                                                                   
Sender280: START
id=5,rate=240.00,total messages=1200,Snapshot period=5,threads=276                                    
ControlThread1: threads=280,fastest_conn=200,slowest_conn=1204,avg_conn=217                           
ControlThread1: Fatal Error.                                                                          
java.lang.NullPointerException                                                                        
        at com.ibm.uk.hursley.perfharness.cmd.SocketCommandProcessor.sendMessage(SocketCommandProcessor.java:122)
        at com.ibm.uk.hursley.perfharness.ControlThread.startWorkers(ControlThread.java:720)          
        at com.ibm.uk.hursley.perfharness.ControlThread.startWorkers(ControlThread.java:736)          
        at com.ibm.uk.hursley.perfharness.ControlThread.run(ControlThread.java:251)                   
Sender272: STOP
...