Preface

I’m used to run telnet to do a quick check if a remote server is reachable and listening on a specific port. When trying this on i5/OS with telnet CMD you may get headache! After some research I ended up with openssl in PASE to succeed my task on IBM i (AS400).

telnet vs openssl syntax

On Telnet 5250 Command Line you first have to enter PASE using

call qp2term

Then run

openssl s_client -connect <server>:<port></pre>

instead of

telnet <server> <port>

as it is not installed in PASE.

Examples

Success, with server using SSL

with openssl

openssl s_client -connect google.at:443  
CONNECTED(00000003)                      
:
---                                      
Certificate chain                        
:
---                                      
New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES128-GCM-SHA256  
Server public key is 2048 bit                            
Secure Renegotiation IS supported                        
:
---            
read:errno=0   
$

with telnet

me@somewhere:~$ telnet google.at 443
Trying 216.58.214.67...
Connected to google.at.
Escape character is '^]'.
^]
telnet> quit
Connection closed.

Failure

with openssl

openssl s_client -connect google.at:1234   
:
: ...timeout is about a minute
:
connect: Connection timed out              
connect:errno=78                           
$

with telnet

me@somewhere:~$ telnet google.at 4321
Trying 216.58.214.67...
^C

Success, with server not using SSL

with openssl

openssl s_client -connect google.at:80                                                           
CONNECTED(00000003)                                                                              
:
---                                                                                              
no peer certificate available                                                                    
---                                                                                              
:
---                                                                                              
New, (NONE), Cipher is (NONE)                                                                    
Secure Renegotiation IS NOT supported                                                            
:
---                            
$

with telnet

me@somewhere:~$ telnet google.at 80
Trying 216.58.214.67...
Connected to google.at.
Escape character is '^]'.
^]
telnet> quit
Connection closed.

Testing Remote TCP/IP Connectivity on IBM i (AS400)

Table of contents

Preface

telnet vs openssl syntax

Examples

Success, with server using SSL

with openssl

with telnet

Failure

with openssl

with telnet

Success, with server not using SSL

with openssl

with telnet