Program works with older libssl, but not with newer

[Christoph Pleger]

Hello,

> > I have here a self-written server program and the corresponding
> > self-written client program. These run well together with libssl 1.1.0l,
> > but with libssl 1.1.1d, the same programs give errors SSL_ERROR_SYSCALL
> > in SSL_read(), no matter if I recompile the programs and then run them,
> > or just replace libssl with the newer version.
> 
> OpenSSL 1.1.1 supports TLS 1.3, which OpenSSL 1.1.0 did not.
> 
> > So, I want to ask if there are any known incompabilities in the libssl
> > versions that require me to change the code of the programs, or if there
> > is
> > any known bug in libssl1.1.1d that may cause the mentioned errors.
> 
> Use of TLS 1.3 changes the communication patterns of the TLS protocol in
> some non-trivial ways, and, if your application were fragile, it might
> have gotten by with TLS 1.2, but the latent bugs could show up with TLS
> 1.3.

Now, I replaced TLS_server_method() and TLS_client_method() with 
TLSv1_2_server_method() and TLSv1_2_client_method() respectively, and the same 
error occurs. 

Regards
  Christoph