Having had a quick look at the port 30003 data lines, this is my best guess at the data:
MSG - just a label
3 - This is the message type, all lines are MSG 3 at present
0 - ?
0 - ?
Mode S Code - e.g. 400928
0 - ?
Date - in the format 2008/03/27
Time - in the format 14:12:42.750
Date - don't know why this appears a second time
Time - another time field, identical to the earlier time
Flight ID - e.g. EZT945X
Altitude - in feet
Groundspeed - in knots
Heading - degrees magnetic (could be track rather than heading)
Latitude - in the form 52.5177, positive is North
longitude - in the form -1.9658, negative is West
Vertical rate - positive for climb, negative for descent
Squawk - four figure Mode 3 code between 0000-7777
0 - ?
0 - ?
0 - ?
0 - ?
Each data field in comma delimited and each data line has a CR+LF at the end. For simple manipulation, it's very easy to import the captured txt file into Excel.