stunnel client fails to open connection

I have stunnel4 configured as client installed on Linux Mint 17.1 Rebecca x64, which is based on Ubuntu Trusty. It fails to work and I see no reason for it to fail. Logging with debug=7 shows the following:

2015.05.10 07:43:13 LOG7[20236:140482487383872]: Clients allowed=500
2015.05.10 07:43:13 LOG5[20236:140482487383872]: stunnel 4.53 on x86_64-pc-linux-gnu platform
2015.05.10 07:43:13 LOG5[20236:140482487383872]: Compiled with OpenSSL 1.0.1e 11 Feb 2013
2015.05.10 07:43:13 LOG5[20236:140482487383872]: Running with OpenSSL 1.0.1f 6 Jan 2014
2015.05.10 07:43:13 LOG5[20236:140482487383872]: Update OpenSSL shared libraries or rebuild stunnel
2015.05.10 07:43:13 LOG5[20236:140482487383872]: Threading:PTHREAD SSL:+ENGINE+OCSP Auth:LIBWRAP Sockets:POLL+IPv6
2015.05.10 07:43:13 LOG5[20236:140482487383872]: Reading configuration from file /etc/stunnel/stunnel.conf
2015.05.10 07:43:13 LOG7[20236:140482487383872]: Compression not enabled
2015.05.10 07:43:13 LOG7[20236:140482487383872]: PRNG seeded successfully
2015.05.10 07:43:13 LOG6[20236:140482487383872]: Initializing service section [telnets]
2015.05.10 07:43:13 LOG7[20236:140482487383872]: Certificate: /etc/ssl/certs/stunnel.pem
2015.05.10 07:43:13 LOG7[20236:140482487383872]: Certificate loaded
2015.05.10 07:43:13 LOG7[20236:140482487383872]: Key file: /etc/ssl/certs/stunnel.pem
2015.05.10 07:43:13 LOG7[20236:140482487383872]: Private key loaded
2015.05.10 07:43:13 LOG7[20236:140482487383872]: SSL options set: 0x00000004
2015.05.10 07:43:13 LOG6[20236:140482487383872]: Initializing service section [dsp3270s]
2015.05.10 07:43:13 LOG7[20236:140482487383872]: Certificate: /etc/ssl/certs/stunnel.pem
2015.05.10 07:43:13 LOG7[20236:140482487383872]: Certificate loaded
2015.05.10 07:43:13 LOG7[20236:140482487383872]: Key file: /etc/ssl/certs/stunnel.pem
2015.05.10 07:43:13 LOG7[20236:140482487383872]: Private key loaded
2015.05.10 07:43:13 LOG7[20236:140482487383872]: SSL options set: 0x00000004
2015.05.10 07:43:13 LOG5[20236:140482487383872]: Configuration successful
2015.05.10 07:43:13 LOG7[20236:140482487383872]: Service [telnets] (FD=12) bound to 0.0.0.0:3141
2015.05.10 07:43:13 LOG7[20236:140482487383872]: Service [dsp3270s] (FD=13) bound to 0.0.0.0:7490
2015.05.10 07:43:13 LOG7[20242:140482487383872]: Created pid file /stunnel4.pid
2015.05.10 08:50:13 LOG7[20242:140482487383872]: Service [telnets] accepted (FD=3) from 127.0.0.1:47623
2015.05.10 08:50:13 LOG7[20242:140482487543552]: Service [telnets] started
2015.05.10 08:50:13 LOG7[20242:140482487543552]: Waiting for a libwrap process
2015.05.10 08:50:13 LOG7[20242:140482487543552]: Acquired libwrap process #0
2015.05.10 08:50:13 LOG3[20242:140482487543552]: Unexpected socket close (read_blocking)
2015.05.10 08:50:13 LOG5[20242:140482487543552]: Connection reset: 0 byte(s) sent to SSL, 0 byte(s) sent to socket
2015.05.10 08:50:13 LOG7[20242:140482487543552]: Local socket (FD=3) closed
2015.05.10 08:50:13 LOG7[20242:140482487543552]: Service [telnets] finished (0 left)
2015.05.10 08:50:13 LOG7[20242:140482487543552]: str_stats: 1 block(s), 32 data byte(s), 58 control byte(s)

So for some reason there is a problem immediately after accepting a connection and starting a service. The service is a simple pass-thru:

[telnets]
accept = 3141
connect = 192.168.80.5:992

The log shows that stunnel was build for an earlier OpenSSL release, is this a possible cause of the problem? How do I get this working?

Dave