Get bytes sent to client

Hello.
I'd like to collect some statistics in my application (using JDBC). In
Oracle I could collect data, sent to client, using the following query:

SELECT S.value FROM V$MYSTAT S,SYS.V_$STATNAME NAMES
WHERE NAMES.STATISTIC#=S.STATISTIC#
AND NAMES.NAME='bytes sent via SQL*Net to client';

Can I do something like this in PostgreSQL?
I was suggested to wrap some parts of PostgreSQL JDBC Driver, but it
looks not very good.
Is there any other way to count up raw data, received by client (or sent
by server)?
The purpose is to estimate bandwidth from client to DBMS and size of
query responses...
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Best regards,
Alexander Pyhalov,
system administrator of Computer Center of South Federal University