Archive for the ‘Communications Development’ Category
Posted by jpluimers on 2025/12/10
A while ago I got an error 103 using both Beyond Compare. That did not whos the connection log or error reason, but WinSCP did: it mentioned unexpected output during the logon.
I got reminded that I had already solved this error before via [Wayback/Archive] SSH login works but SFTP login doesn’t – Server Fault (thanks [Wayback/Archive] qreon and [Wayback/Archive] Paulus):
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Posted in *nix, *nix-tools, bash, bash, Beyond Compare, Communications Development, Development, Internet protocol suite, Power User, Scripting, SFTP, Software Development, SSH, TCP, Windows, WinSCP | Leave a Comment »
Posted by jpluimers on 2025/12/09
For my link archive a router I bought a few years back: [Wayback/Archive] GL-SFT1200 Secure Wi-Fi Router On The Go – AC1200 Dual-Band Gigabit Wireless Internet Router | IPv6 | USB 2.0 | MU-MIMO | 128MB RAM | Repeater Bridge | Access Point-M Mode: Amazon.de: Computer & Accessories
- It is USB-C powered (the power brick delivers 3A at 5V, but in reality it uses far less).
- Mode and reset buttons are behind the antenna (see picture below).
- It is specced as AC1200, but that’s just theoretical a number.
- It came with EU and UK plug.
I needed it because from prior experience, I knew GL.iNEt can support a special Wireless Repeater mode where it still functions as a router (hiding the LAN/WLAN behind NAT)

Two physical drawbacks likely due to the portable nature:
the plastic RJ45 ports are slightly too wide which means that these keep falling out [Wayback/Archive] Inline® Dust cover, for RJ45 socket, color: green, 100pcs. Pack: Amazon.de: Electronics & Photo
- no holes in the base to hang it to a wall
One firmware drawback: it shipped with v3.212 for which I could not find release notes. Luckily the firmware v3.215 I upgraded to had: [Wayback/Archive] Firmware v3.215 is released – Technical Support – GL.iNet.
Links to product and manuals (the paper manual are just two thin sheets, but the on-line documentation is OK; I was surprised WireGuard and Tor were supported!):
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Posted in Communications Development, Development, DHCP, Ethernet, GL.iNet, GL.iNET GL-SFT1200, Hardware, Internet protocol suite, Network-and-equipment, Power User, routers, UDP, WiFi, Windows, WinSCP | Leave a Comment »
Posted by jpluimers on 2025/11/14
The plan was to run a Postfix secondary MX inside a docker container.
Below are many links that might help me to get that going.
For now, I think this is the shortlist of solutions to try:
- Docker Mailserver
- Mailcow
- Mailu
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Posted in *nix, *nix-tools, Cloud, Communications Development, Containers, Development, Docker, Infrastructure, Internet protocol suite, Kubernetes (k8n), postfix, Power User, SMTP | Tagged: 254, 29, 52, 787, DMARC, domains, set | Leave a Comment »
Posted by jpluimers on 2025/11/12
This finally made me perform the (long overdue) migration from Sendmail to Postfix:
The Sender Rewriting Scheme (SRS) is a technique to forward mails from domains which deploy the Sender Policy Framework (SPF) to prohibit other Mail Transfer Agents (MTAs) from sending mails on their behalf. With SRS, an MTA can circumvent SPF restrictions by replacing the envelope sender with a temporary email address from one of their own domains. This temporary address is bound to the original sender and only valid for a certain amount of time, which prevents abuse by spammers.
[Wayback/Archive] roehling/postsrsd: Postfix Sender Rewriting Scheme daemon
Via a long queste to figure out why Gmail every now and then bounces forwarded messages because of Sender Policy Framework (SPF). Below are a few of the links that brought me here in mostly reverse order, but first some links that should help me further on the topic of Postfix virtual aliases.
The sendmail setup had some features not covered below (like a catch-all forward for email to addresses virtual domains not covered by a virtual alias) which I hopefully can cover later.
One thing learned both over the past decades and related postfix material: use separate servers or containers for each of your functions. So do not mix web-hosting, outgoing mail, incoming mail, fail2ban and others on the same server.
Links:
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Posted in *nix, *nix-tools, Communications Development, Development, Internet protocol suite, postfix, Power User, sendmail, SMTP | Tagged: Reload | Leave a Comment »
Posted by jpluimers on 2025/10/28
For my link archive initiated because I was trying to find out why ADS-B Exchange does not list originating and destination airports for flights, then on how to get at that data.
It is grouped in a few parts, starting with:
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Posted in Communications Development, Development, HTTP, Internet protocol suite, JavaScript/ECMAScript, JSON, REST, Scripting, Software Development, TCP, Web Development | Leave a Comment »
Posted by jpluimers on 2025/08/26
Last week I wrote about Example how not to return a HTPP-500 result: Amazon DE – Tut uns Leid!.
Today I found https://archive.is/undefined which consistently returns a HTTP 404 in the HTTP result.
It reminded me of an old (well, what is old anyway <g>) post Best 404 page ever. back in the days (returning both 404 in the HTTP result and page content) I did not yet archive outgoing links (it took me a few more years to realise many URLs are ephemeral and have queued up a post on that for early next year), and found out the site has changed since then. Time for archived and updated links, and a repository too as by now the source has been published on GitHub:
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Posted in Communications Development, Development, HTML, HTTP, Internet protocol suite, Software Development, Web Development | Leave a Comment »
Posted by jpluimers on 2025/08/13
[Wayback/Archive] GS305E | Easy Smart Managed Essentials Switch | NETGEAR Support which can do many-to-one port mirroring.
This is a newer and cheaper hardware revision than the:
- GS105Ev2 (which is managed and can do port-mirroring, and is confusingly sold as GS105E-200) which in Germany already is end-of-life
- GS105Ev1 (which is unmanaged and cannot do port-mirroring and is confusingly sold as GS105E-100) which is end-of-life but still sold
Via [Wayback/Archive] Everyone Should Have One of These – EASY Packet Capture! – YouTube who explains very well why you need a switch that can do port-mirroring, then recommends the GS105E but forgets to mention:
- there are different revisions of the GS105E with the above drawbacks
- there is GS305E
Related:
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Posted in Blue team, Communications Development, Development, Ethernet, Hardware, Internet protocol suite, Network-and-equipment, Power User, Red team, Security, Software Development, TCP, UDP | Leave a Comment »
Posted by jpluimers on 2025/08/07
On my research list [Wayback/Archive] html – What can cause Chrome to give an net::ERR_FAILED on cached content against a server on localhost? – Stack Overflow
The reason what that back then this would fail (but worked in Firefox and Safari, and because I was in a hurry I didn’t research further): [Wayback/Archive] https://www.office.com/
This site can’t be reached
The webpage at https://www.office.com/ might be temporarily down or it may have moved permanently to a new web address.
ERR_FAILED
Thanks [Wayback/Archive] Mason Wheeler and [Wayback/Archive] Joel Davey.
Details:
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Posted in Chrome, Communications Development, Development, Encryption, HTTP, https, HTTPS/TLS security, Power User, Security, TCP, TLS, Web Browsers, Web Development | Leave a Comment »
Posted by jpluimers on 2025/08/06
Sometimes I need [Wayback/Archive] Redirect Checker | Check your Statuscode 301 vs 302 on the command-line, so cURL to the rescue: [Wayback/Archive] linux – Get final URL after curl is redirected – Stack Overflow. The relevant portions of answers and comments further below.
TL;DR:
Since I prefer verbose command-line arguments (you can find them at the [Wayback/Archive] curl – How To Use on-line man page) especially in scripts this HTTP GET request is what works with Twitter:
% curl --location --silent --output /dev/null --write-out "%{url_effective}\n" https://twitter.com/anyuser/status/20
https://x.com/anyuser/status/20
This failed (twitter dislikes HTTP HEAD requests):
% curl --head --location --silent --output /dev/null --write-out "%{url_effective}\n" https://twitter.com/anyuser/status/20
https://twitter.com/anyuser/status/20
Notes
Given so many of my scripts now run on zsh, I added the new-line because of command line – Why does a cURL request return a percent sign (%) with every request in ZSH? – Stack Overflow. You can strip that bit.
Note that these do not perform client side redirects, so they do not return the ultimate originating URL https://x.com/jack/status/20 (which was the first ever Tweet on what was back then called twttr) as Twitter on the client-side overwrites window.location.href with the final URL. Similar behaviour for getting the Twitter user handle of a Twitter user ID, more on Twitter tricks below.
Tweet by TweetID trick via [Wayback/Archive] Accessing a tweet using only its ID (and without the Twitter API) – Bram.us.
Further reading (thanks [Wayback/Archive] vise, [Wayback/Archive] Daniel Stenberg, [Wayback/Archive] Ivan, [Wayback/Archive] AndrewF, [Wayback/Archive] Roger Campanera, and [Wayback/Archive] Dave Baird):
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Posted in *nix, *nix-tools, bash, Batch-Files, Bookmarklet, Communications Development, Conference Topics, Conferences, CSS, cURL, Development, Event, HTTP, Internet protocol suite, JavaScript/ECMAScript, Power User, Scripting, SocialMedia, Software Development, TCP, Twitter, Web Browsers, Web Development | Tagged: 76 | Leave a Comment »