[ADMIN] Error FATAL: invalid frontend message type 21

Hi,

What could be the cause for error message, FATAL:  invalid frontend
message type 21?
My application notices that the postgres connection is gone and it
reconnects, but i'm wondering what could cause this?

I've  connected with odbc (unixodbc), unixsockect and using localhost, i
always see this message.


Running postgresql in debian 8, version:

ii  libpq5:amd64 9.4.13-0+deb8u1                    amd64       
PostgreSQL C client library
ii  postgresql-9.4 9.4.13-0+deb8u1                    amd64       
object-relational SQL database, version 9.4 server
ii  postgresql-client-9.4 9.4.13-0+deb8u1                   
amd64        front-end programs for PostgreSQL 9.4


conf:
# -----------------------------
# PostgreSQL configuration file
# -----------------------------

data_directory = '/var/lib/postgresql/9.4/main'
hba_file = '/etc/postgresql/9.4/main/pg_hba.conf'
ident_file = '/etc/postgresql/9.4/main/pg_ident.conf'
external_pid_file = '/var/run/postgresql/9.4-main.pid'

# - Connection Settings -
listen_addresses = '127.0.0.1'
port = 5432
max_connections = 100
unix_socket_directories = '/var/run/postgresql'
ssl = false
shared_buffers = 128MB
dynamic_shared_memory_type = posix

log_destination = 'syslog'
syslog_facility = 'LOCAL0'
syslog_ident = 'postgres'
log_line_prefix = '%t [%p-%l] %q%u@%d '
log_timezone = 'localtime'
stats_temp_directory = '/var/run/postgresql/9.4-main.pg_stat_tmp'
datestyle = 'iso, mdy'
timezone = 'localtime'
lc_messages = 'C'
lc_monetary = 'C'
lc_numeric = 'C'
lc_time = 'C'
default_text_search_config = 'pg_catalog.english'



--
Saludos / Regards / Cumprimentos
António Silva