QuickFix - messages out of sequence

Question

What could cause a message to sent out of sequence like this?

20150731-12:42:46.096 : 8=FIX.4.2^A9=57^A35=0^A34=1400^A49=erio123^A52=20150731-12:42:46.094^A56=B^A10=014^A
20150731-12:43:00.916 : 8=FIX.4.2^A9=207^A35=D^A34=1401^A49=erio123^A52=20150731-12:43:00.916^A56=I
20150731-12:43:31.019 : 8=FIX.4.2^A9=57^A35=0^A34=1402^A49=erio123^A52=20150731-12:43:31.015^A56=B^A10=004^A
20150731-12:44:01.048 : 8=FIX.4.2^A9=207^A35=D^A34=1404^A49=erio123^A52=20150731-12:44:01.048^A56
20150731-12:44:01.048 : 8=FIX.4.2^A9=57^A35=0^A34=**1403**^A49=erio123^A52=20150731-12:44:01.023^A56=B^A10=002^A
20150731-12:44:01.116 : 8=FIX.4.2^A9=102^A35=4^A34=1403^A43=Y^A49=
20150731-12:44:32.067 : 8=FIX.4.2^A9=57^A35=0^A34=1405^A49=
20150731-12:45:02.079 : 8=FIX.4.2^A9=57^A35=0^A34=1406^A49=

Answer 1

Those two messages weren't sent out of sync, they were sent at the same millisecond. This can happen occasionally when sending lots of messages in a short time due to network latency; you have to reorder them on the receiving side.