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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘Communications Development’ Category

Tools for TCP tunnels over HTTP/HTTPS

Posted by jpluimers on 2019/01/16

With the advent of WebSockets, it looks like TCP tunnels over HTTP/HTTPS are gaining more ground and I need to put some research time in them.

Some old to new links:

CONNECT requests are not supported by many HTTP proxies, especially in larger organisations, so chisel and crowbar have a much bigger chance there.

And of course there is SoftEtherVPN/SoftEtherVPN: A Free Cross-platform Multi-protocol VPN Software. * For support, troubleshooting and feature requests we have For critical vulnerability please email us. (mail address is on the header.).

However, that is a VPN solution which is much broader than just a single TCP tunnel. You can so similar things with OpenVPN, but over HTTP/HTTPS, also requires CONNECT:

SoftEtherVPN seems to be more versatile though. I blogged about that before, but back then didn’t have needs for it yet. VPN over HTTPS: Ultimate Powerful VPN Connectivity – SoftEther VPN Project.


via: [WayBackVPN through only http – Server Fault answer by [WayBack] neutrinus

Posted in Communications Development, Development, HTTP, https, Internet protocol suite, Network-and-equipment, OpenVPN, Power User, TCP, VPN, WebSockets, Windows-Http-Proxy | Leave a Comment »

Need to put some research in Google Calendar support for EXRULE and EXDATE

Posted by jpluimers on 2019/01/15

Though the Google Calendar UI does not support EXRULE and EXDATE to exclude certain slots (via dates or rules) from recurring events.

The API supports them: [WayBackGoogle Calendar API, RRULE and EXDATE – Stack Overflow


Posted in Communications Development, Development, Google, GoogleCalendar, HTTP, Internet protocol suite, Power User, REST, TCP | Leave a Comment »

Testing SMTP from the console on Linux, BSD and Mac OS: swaks and smtp-cli Perl script clients

Posted by jpluimers on 2019/01/03

Testing SMTP using telnet is tedious as you have to remember the commands and responses in the SMTP protocol. It gets even harder when doing SMTP AUTH, as then you have to base encode a bunch of strings [WayBackHow to Test SMTP AUTH using Telnet [Wiki] | NDCHost

Luckily there is a Perl script swaks: [WayBackSwaks – Swiss Army Knife for SMTP which does ESMTP and LMTP as well as TLS.

The funny thing is that the repository at jetmore/swaks: Swaks – Swiss Army Knife for SMTP only has the readme, but the not the script which you can get from [WayBack]

Despite that, most Linux distributions have an installation package.

[WayBackswaks for OpenSuse is in the [WayBacknetwork repository, so for Tumbleweed (actually: Factory) on Raspberry Pi you need to perform this:

zypper addrepo
zypper refresh
zypper install swaks

On Mac OS X it is even easier: if you have the homebrew package manager installed, you just install the [WayBackswaks formula using the [WayBack] swaks.rb script:

brew install swaks

Note there is also the smtp-cli Perl script which I mentioned before at Fake/Mock SMTP servers and services for use during development, which also does TLS, but few environments have ready built packages for them. If you still want to try it out:


swaks -tls --to --from --server --auth-user username

Which prompts for the password, then outputs like this:

=== Trying
=== Connected to
<- 220 ESMTP ESMTP server ready -> EHLO rmbpro1tbjwp
<- hello [], pleased to meet you
<-  250-HELP
<-  250-SIZE 157286400
<-  250-8BITMIME
<-  250-STARTTLS
<- 250 OK -> STARTTLS
<- 220 Ready to start TLS === TLS started with cipher TLSv1:DHE-RSA-AES256-SHA:256 === TLS no local certificate set === TLS peer DN="/OU=Domain Control Validated/OU=PositiveSSL Wildcard/CN=*" ~> EHLO rmbpro1tbjwp
<~ hello [], pleased to meet you
<~  250-HELP
<~  250-SIZE 157286400
<~  250-8BITMIME
<~ 250 OK ~> AUTH LOGIN
<~ 334 ############ ~> anA=
<~ 334 ############ ~> ############################
<~ 235 ... authentication succeeded ~> MAIL FROM:<>
<~  250 <> sender ok
 ~> RCPT TO:<>
<~  250 <> recipient ok
 ~> DATA
<~ 354 enter mail, end with "." on a line by itself ~> Date: Wed, 19 Jul 2017 09:09:57 +0200
 ~> To:
 ~> From:
 ~> Subject: test Wed, 19 Jul 2017 09:09:57 +0200
 ~> Message-Id: <20170719090957.052207@rmbpro1tbjwp>
 ~> X-Mailer: swaks v20170101.0
 ~> This is a test mailing
 ~> .
<~ 250 accepted mail mXA71v00C4jr6ac01XA9Bo for delivery ~> QUIT
<~  221 ESMTP closing connection
=== Connection closed with remote host.


Posted in *nix, *nix-tools, Communications Development, Development, Hardware Development, Internet protocol suite, Linux, openSuSE, Power User, Raspberry Pi, SMTP, SuSE Linux, Tumbleweed | Leave a Comment »

How to Setup Chroot SFTP in Linux (Allow Only SFTP, not SSH)

Posted by jpluimers on 2018/12/24

If you want to setup an account on your system that will be used only to transfer files (and not to ssh to the system), you should setup SFTP Chroot Jail.

This explains how: [WayBack] How to Setup Chroot SFTP in Linux (Allow Only SFTP, not SSH)

Posted in *nix, *nix-tools, Communications Development, Development, Internet protocol suite, Power User, SFTP, SSH, TCP | Leave a Comment »

on my research list: autossh

Posted by jpluimers on 2018/12/12

Having mainly used ssh as a means to connect to a shell on remote machines and occasionally a manual port forward.

I never noticed autossh where you can automate the ssh logon process to keep permanent port forwards up and running. Cool!

It’s on my research list now, as this will be useful probably sooner than later:

My initial impression is that autossh is a wrapper around the regular ssh client that allows reconnection upon communication failures.


Posted in *nix, *nix-tools, Communications Development, Development, Internet protocol suite, Power User, SSH, TCP | Leave a Comment »

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