An error like this might be returned if you will try to connect to a port which is actually not the port DB2 server listens on.
E.g. if I would, by mistake, try to connect to port 22 (ssh) I will get the same error:
$ java com.ibm.db2.jcc.DB2Jcc -url jdbc:db2://localhost:22/SAMPLE -user db2v111 -password passw0rd
[jcc]Command : java com.ibm....
You can use a subquery with the same table in both the primary and sub queries, join on trade_id = keyword_value
Depending on how many levels a trade could have it might get complex, but this should get you going in the right direction.