How can I be confirm that data is encrypted over the network using SSL

I have configured SSL connection between client/server using self-signed
certificate.

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SSL connection (cipher: DHE-RSA-AES256-SHA, bits: 256)

postgres=# \l
List of databases
Name | Owner | Encoding
-----------+----------+----------
postgres | postgres | UTF8
template0 | postgres | UTF8
template1 | postgres | UTF8
(3 rows)
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PGDATA dir:

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-bash-3.2$ ls -l
total 84
drwx------ 5 postgres postgres 4096 May 4 14:09 base
drwx------ 2 postgres postgres 4096 May 5 10:58 global
...
-rw------- 1 postgres postgres 3600 May 4 14:17 server.crt
-rw------- 1 postgres postgres 887 May 4 14:17 server.key
-rw------- 1 postgres postgres 2195 May 4 14:16 server.req

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Client ~/.postgresql dir

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-bash-3.2$ ls -l
total 12
-rw-r--r-- 1 postgres postgres 3259 May 4 18:36 postgresql.crt
-rw------- 1 postgres postgres 887 May 4 18:35 postgresql.key
-rw-r--r-- 1 postgres postgres 2080 May 4 18:35 postgresql.req

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I set the $PGSSLMODE=require to encrypt data across the netwrok.

How could I be sure that data is encrypted over the network?