Hi,

I have been using stunnel for quite a long time on macOS without any problems. Specifically, I use this to connect to an nntps server. This is the corresponding config section:

| [nntp2] | client = yes | accept = 127.0.0.2:1119 | connect = news.individual.de:563

With 5.50 everything goes well:

| 2019.04.06 10:48:05 LOG5[2]: Service [nntp2] accepted connection from 127.0.0.2:49366 | 2019.04.06 10:48:05 LOG5[2]: s_connect: connected 130.133.4.10:563 | 2019.04.06 10:48:05 LOG5[2]: Service [nntp2] connected remote server from 192.168.200.102:49367

I can read news without further log entries.

After the upgrade to 5.51 I can not read any news anymore. As soon as I want to read an article the connection breaks down:

| 2019.04.06 10:54:09 LOG5[0]: Service [nntp2] accepted connection from 127.0.0.2:49189 | 2019.04.06 10:54:09 LOG5[0]: s_connect: connected 130.133.4.10:563 | 2019.04.06 10:54:09 LOG5[0]: Service [nntp2] connected remote server from 192.168.200.102:49190 | 2019.04.06 10:54:19 LOG3[0]: transfer() loop executes not transferring any data | 2019.04.06 10:54:19 LOG3[0]: please report the problem to Michal.Trojnara@stunnel.org | 2019.04.06 10:54:19 LOG3[0]: stunnel 5.51 on x86_64-apple-darwin18.5.0 platform | 2019.04.06 10:54:19 LOG3[0]: Compiled/running with OpenSSL 1.1.1b 26 Feb 2019 | 2019.04.06 10:54:19 LOG3[0]: Threading:PTHREAD Sockets:POLL,IPv6 TLS:ENGINE,FIPS,OCSP,PSK,SNI | 2019.04.06 10:54:19 LOG3[0]: protocol=TLSv1.2, SSL_pending=0 | 2019.04.06 10:54:19 LOG3[0]: sock_open_rd=Y, sock_open_wr=Y | 2019.04.06 10:54:19 LOG3[0]: SSL_RECEIVED_SHUTDOWN=n, SSL_SENT_SHUTDOWN=n | 2019.04.06 10:54:19 LOG3[0]: sock_can_rd=n, sock_can_wr=n | 2019.04.06 10:54:19 LOG3[0]: ssl_can_rd=n, ssl_can_wr=n | 2019.04.06 10:54:19 LOG3[0]: read_wants_read=Y, read_wants_write=n | 2019.04.06 10:54:19 LOG3[0]: write_wants_read=n, write_wants_write=n | 2019.04.06 10:54:19 LOG3[0]: shutdown_wants_read=n, shutdown_wants_write=n | 2019.04.06 10:54:19 LOG3[0]: socket input buffer: 0 byte(s), TLS input buffer: 0 byte(s) | 2019.04.06 10:54:19 LOG5[0]: Connection reset: 2151 byte(s) sent to TLS, 3546 byte(s) sent to socket | 2019.04.06 10:54:21 LOG5[1]: Service [nntp2] accepted connection from 127.0.0.2:49191 | 2019.04.06 10:54:21 LOG5[1]: s_connect: connected 130.133.4.10:563 | 2019.04.06 10:54:21 LOG5[1]: Service [nntp2] connected remote server from 192.168.200.102:49192 | 2019.04.06 10:54:23 LOG3[1]: transfer() loop executes not transferring any data | 2019.04.06 10:54:23 LOG3[1]: please report the problem to Michal.Trojnara@stunnel.org | 2019.04.06 10:54:23 LOG3[1]: stunnel 5.51 on x86_64-apple-darwin18.5.0 platform | 2019.04.06 10:54:23 LOG3[1]: Compiled/running with OpenSSL 1.1.1b 26 Feb 2019 | 2019.04.06 10:54:23 LOG3[1]: Threading:PTHREAD Sockets:POLL,IPv6 TLS:ENGINE,FIPS,OCSP,PSK,SNI | 2019.04.06 10:54:23 LOG3[1]: protocol=TLSv1.2, SSL_pending=0 | 2019.04.06 10:54:23 LOG3[1]: sock_open_rd=Y, sock_open_wr=Y | 2019.04.06 10:54:23 LOG3[1]: SSL_RECEIVED_SHUTDOWN=n, SSL_SENT_SHUTDOWN=n | 2019.04.06 10:54:23 LOG3[1]: sock_can_rd=n, sock_can_wr=n | 2019.04.06 10:54:23 LOG3[1]: ssl_can_rd=n, ssl_can_wr=n | 2019.04.06 10:54:23 LOG3[1]: read_wants_read=Y, read_wants_write=n | 2019.04.06 10:54:23 LOG3[1]: write_wants_read=n, write_wants_write=n | 2019.04.06 10:54:23 LOG3[1]: shutdown_wants_read=n, shutdown_wants_write=n | 2019.04.06 10:54:23 LOG3[1]: socket input buffer: 0 byte(s), TLS input buffer: 0 byte(s) | 2019.04.06 10:54:23 LOG5[1]: Connection reset: 163 byte(s) sent to TLS, 435 byte(s) sent to socket

Downgrading to 5.50 solves this issue for the time being. Are there any changes between 5.50 and 5.51 that could explain this behavior?

Dennis