Beej's Guide to Network Programming (1994-2020) | Hacker News Reader

Beej's Guide to Network Programming (1994-2020)

beej.us

993 pointsColinWright165 comments

All your kind words are literally bringing tears to my eyes--thank you!

My current plan is to keep writing freely-available guides for as long as I can reach the keyboard. And maybe even longer with what will undoubtedly be awesome futuristic speech recognition--or mind-reading! That's not scary at all!

I'm leaning on bash/zsh scripting one I finish the utterly gigantic C guide I'm on now... hopefully later this year. But I'm always open to suggestion for topics... :)

You have touched so many people and have created real value with your work

This guide was instrumental in letting me understand sockets and network programming. I've probably recommended it to at least a hundred other people over the years.

You have made a huge positive impact.

Thank you.

Your guide single-handedly got me through network programming in C at university. This was back in the early 2000s. Thank you! And I'm so happy to see your guide still getting updated.

How funny - it got me through the same course but barely 2-3 years ago.

It just got me through my first project in a class this semester! I suspect it will be assisting students for quite some time to come.

Your original document was the quintessential resource for me in the 90s. Heartfelt thank you for putting me on track back then. Highly appreciated!

I've pointed so many folks over the years to your guide.

Keep up the great work.

P.S. Each time I do refer folks over or see a thread like this gives me fond memories of the O'Connell labs and the opportunities we had to enjoy networking in the early days.

The fun of the HP bug of the week and running a unix farm with shell accounts for all of us students.

Your page was what bring me into "magical" programming as a teen 20 years ago. Being able to communicate with a remote program on a free shell and actually understand how it works was the best feeling.

This indirectly shaped my life in many ways. Thank you!

you are the definition of hacker for me, thank you for your time, efforts, sense of humour, empathy, existence.

That guide will always be close to me. :)

When was the first edition? I feel like I remember using it in the early 90s ... maybe 1991? The mods have put the dates "1994-2020" in the title, but I feel like I remember it from earlier than that.

Edit:

OK, on 2003/07/06 15:11:16 the wayback machine captured Version 1.5.5 (13-Jan-1999). At the end it says:

Hmm.

Echoing a similar sentiment here, Thank You!!!

Amazing! This guide got me into network programming back when I was still on rural dial-up. It helped me through various programming courses in high school and university, and I still occasionally refer to it from time to time. Thanks for your contributions, they really improved my quality of life!

For the brief amount of time I was your student at Lambda, you made a huge impression. Beyond this tutorial, you're a gifted teacher and inspirational person. Much respect and love!

I'll read your future-brainwave-transmission tutorials, anytime, even if they run the risk of causing minor insanity!

When I was first learning about network programming, I used to pour over your guide (hosted locally on a Chico State account at the time, if I remember correctly), absorbing every detail I could fit into my young mind. That was... more years ago than I want to think about, but I'm glad to see the guide continuing to get updates!

And I'm also glad for the opportunity to directly thank you for the work you've put into this over the years :)

I discovered your guide for the first time today after decades of programming. Light bulbs going off constantly - thank you, not only for clearly elucidating the vital points, but also for the great humour which keeps me firmly grounded in the marvel and insanity of what's been built to connect us all together.

Such topics aren't dry and boring, they're fascinating and inspiring, and it's so valuable that you are able to present them that way.

(Would love to see your take on shell scripting!)

I'll add another big thank you. Your guide was the sole reason I know anything about network programming, and was very valuable even in Python where documentation was(maybe still is) sparse.

Thanks!

You're Beej?! I learned all about socket programming from your guide, back in high school. In college, during a group project, none of us had taken a networking class yet, but I was armed with your guide and I pushed us to make a networked game. It was a great experience, the game worked well, and the networking teacher was brought in to take a look (he was impressed!).

Thank you so much for your time. I hope you realize how useful it's been.

I feel so nostalgic when I read this Beej's Guide. It's a resource that my computer science professor highly recommended back in the early 2000s. The writing is so clear and concise that it's a pleasure to read (as opposed to some dry and technical materials). It's more useful than some textbook that cost hundreds of dollars. It saved me so much time and sleepless nights to figure out how to complete my network programming assignment.

Let me give you a virtual elbow bump! You really made an impact in my academic and professional career!

I just came to say thank you, Beej! Your guide helped me learn networking and network programming. I love learning by example. Your guide was instrumental in my learning.

Thank you Beej. I hope you eventually update your guide for epoll/kqueue etc. on how to check for data async.

your guide literally helped me hack through a networking class i took in college a decade ago. dont work anywhere close to that stack but this brought back memories.

Thank you so much, your guide was so helpful to me back in high school, undergrad and im certain I will be going back to it in the future.

Your guide was what everyone else recommended when I was stumbling around learning networking a couple years back (reversing and reimplementing an iOS framework that used the BSD sockets API–not really the best environment for someone who couldn't tell connect(2) from accept(2)). With your help I was able to get through that and the understanding carried me through college, in some networking classes that were decidably less educational or useful than your writing. Not bad for a document bearing a copyright from years before I was born!

Thank you! It's ever more important to make these core, key, concepts accessible.

We were both at Chico State in comp sci together. I remember you although we didn't know each other. Dude, you do great work! Every time I see your guide mentioned somewhere it always makes remember that time, and puts a smile on my face.

> I'm leaning on bash/zsh scripting one I finish the utterly gigantic C guide I'm on now... hopefully later this year. But I'm always open to suggestion for topics... :)

That would be amazing, I'd love to read a guide over scripting. The only request I would have is a section over sh as well if you do write such a guide.

Sorry for offering to suggest a Romanian translation, and then disappearing on you, I was 16 at that time.

Your book was what got me deeper into programming and networks in general back then, I have a full time job around this now. Thank you!

That brings back some good memories, I learned socket programming thanks to your guide back in high school.

Ended up working in infrastructure so eh, you kinda paved the way for me :)

Hi, thank you for the great resource, I love the clarity and simplicity without the useless "filler" material to artificially increase a book's number of pages.

I looked up the section on classful networking and CIDR and would like to make one addition that is often overlooked: in classful networking, not only are the network sizes fixed, but also where they reside in the IP address room.

E.g., class A networks used 0.0.0.0 – 127.255.255.255 whereas class C networks used 192.0.0.0 – 223.255.255.255.

With CIDR notation, not only can you have networks of different size, but they can start at arbitrary addresses.

If people talk about a class C network today, they often falsely relate to a network with 256 addresses - but which is located in the address room of original class A/B/D/E networks, for example.

Back in 2010 I had my first embedded programming job. I needed to do some network programming in C (controlling a PLC over ethernet). My boss at the time told me "just read Beej's guide and you'll be fine". He was right. That system is running 24/7 since then.

Good to see that the guide is still being updated.

edit: typo

Same here, my first job out of university was network programming on embedded Linux and Beej's guide was an invaluable resource.

Are you guys me? Exact same story. Network programming on embedded systems. Beej to the rescue.

Same here. That book and the Linux api book are just invaluable resources.

Which linux api book?

The linux programming interface by Michael Kerrisk. It’s incredibly good.

I only found this: https://man7.org/tlpi/

Is there any free or low-cost version?

That’s the high-value version, it’s the only legitimate one

You may be able to get it from your local library via an app like Overdrive[0][1]. Some library programs even have a way for you to get free access to Safari Books Online[2] (I'd say most if not all, in the US at least)

My experience has been that there is rarely a backlog on technical materials like this.

[0]: https://www.overdrive.com/

[1]: Example of for the LA public library of what I mean: https://lapl.overdrive.com/search?query=The+Linux+Programmin...

[2]: https://www.spl.org/books-and-media/books-and-ebooks/oreilly...

That's great information, thank you!

Libraries are like the secret weapon of a learner. I don't know why our industry has such a lack of knowledge about this one! I only recently found out about being able to do this myself

(In some ways, we benefit, since there is little pressure for the large publishers not to offer these kinds of things for free via the library system)

Ancedota (and unrelated to the topic of this thread, but interesting none the less I think):

In California, if you go to a state university (but if I recall correctly this doesn't apply to the University of California system, but the CSU system, if I got my facts straight) they must provide a minimum number of copies of each textbook / reading material required for a class be available via the campus library.

I hardly paid for books once I found this out. I just coordinated with others to make sure it was available when needed. Worked well for me.

I could be hazy on the regulation on this though, it might have just been dumb luck that the two places I went to school had this as a policy, but I remember it being explained as I did above.

How does this book compare to Advanced Programming in the Unix Environment? http://www.apuebook.com/about3e.html

Heck, I passed my uni network programming courses thanks to Beej. It also helped tremendously that our professor was a seasoned UNIX programmer and during lectures he actually typed in his own code and ran it.

I had a few maths lectures who were highly regarded for turning up and proving things from memory in front of the blackboard. I hadn’t really considered that it might be done in CS.

The best lecturer I had in maths would screw up the proofs every time from memory, but the way he screwed them up taught me a lot more than if he'd gotten them right.

Did he acknowledge and fix his mistakes? Or it was just you who noticed and fixed them in your mind?

My experience is that they get about 45 minutes into the lecture, realize that there was an error in minute 10 and spend the rest of the period trying to fix it before telling you to check the book for the correct proof.

One professor provided scans of his written notes. For one of the theorems in his notes, he’d stated it, attempted to prove it, failed, crossed out the proof and wrote ‘QED’. At least he was honest enough to include it!

I remember a lecturer of mine having to state and prove a theorem due to Heawood[1]. I think he did it first because the statement was quite unpleasant and not easy to memorise. I found the point of proving things from memory is that to memorise a proof, one must distill it to key ideas with obvious steps in between. This was particularly useful if you might need to reproduce a proof in an exam.

[1] https://en.m.wikipedia.org/wiki/Heawood_number

Heck, my uni's network programming course pointed people to Beej's work.

Same for me only it was mid to late 90's and I was interested in understanding MUD code.

I have fond memories of that guide and it's always a treat when it pops back up.

Yes, I used the guide in 2006 I think or it at least looks similar. I had used it to write a little webserver in C to talk between the Flash UI and the internals of the device. Worked well :)

Past discussions on this classic include:

2017 https://news.ycombinator.com/item?id=13983212

2017 (a bit) https://news.ycombinator.com/item?id=13670971

2016 (a bit) https://news.ycombinator.com/item?id=12402313

2015 https://news.ycombinator.com/item?id=9445692

2015 (a bit) https://news.ycombinator.com/item?id=9623813

2013 https://news.ycombinator.com/item?id=5241220

2009 https://news.ycombinator.com/item?id=584557

2008 https://news.ycombinator.com/item?id=337371 ("Wow, I first read this when I was in high school. It's still being updated?")

Socket programming never clicked for me before I learned about the protocols themselves first. My brain just rejected using an API for something I didn't understand. So if you're like me, I highly recommend reading Comer's "Internetworking with TCP/IP" first, and sitting down to socket programming later.

That's three volumes... Anything shorter you can recommend?

You really only need the first one.

Volume 1 of TCP/IP Illustrated by W. Richard Stevens is a good one. If you're very pressed for time, start with the picture of the TCP state machine and work outwards.

Maybe it's just me but it took a long time before I found another "big" API as horrible as BSD sockets is.

Well, some APIs are not meant to be used directly, but hidden behind a class or more application-specific functions.

Maybe, but in C land that high level socket API never materialized in the standard library. And you are right that it is awful. I've been doing network programming for over 20 years now and I still have to look up the manual when making a TCP/UDP connection in C.

I've made my own wrapper a few times but often don't get to use it for various reasons.

  int tcp_connect(char* remote_host, short int port, options* options, static char** error_string);

  int tcp_listen(short int port, options* options, static char** error_string);

  int udp_listen(short int port, options* options, static char** error_string);

Does any necessary lookups for you and connects sets up the socket. The options structure can be NULL if you want the sane defaults, or you can zero it out and set only the options you care about like the connect timeout or flags like SO_REUSEADDR or O_NONBLOCK. Returns the socket number or -1 if an error occurs. In the event of an error the error_string is also set. The _listen variants spit out a socket ready for an accept() call.

If you need something weird then you're back to the low level BSD socket stuff, but this covers about 95% of my use cases. While it's only saving a handful of system calls, it ends up being quite a bit of boilerplate and error handling. Especially if you specify a connect timeout, since that is kind of awkward to do with the BSD socket API.

ptrace(2) comes to mind.

I had the most wonderful déjà vu the other day. I needed to do some serious-ish network programming for the first time in 20 years. I googled around a bit for a refresher. What do I find? Beej's guide – the same Beej's guide that was my first introduction to the topic 20 years prior!

It was wonderfully poetic to me that the same document that taught me how to make a wildly dangerous IRC bot in my teenage room for the lulz also re-taught me the stuff I needed to deliver a low-latency ML offloading demo at my serious(-ish) job 20 years later. Gave me a real warm fuzzy feeling :-)

PS:

HN disucssion anno 2015: https://news.ycombinator.com/item?id=9445692

Anno 2017: https://news.ycombinator.com/item?id=13983212

I thought I'd add: I know that this is a very normal thing in some sense. Many textbooks remain relevant for decades and decades (I'm a mathematician, we know this perhaps better than most). But still, it's rarely the case for an online document – one about computer technology even more so!

> It was wonderfully poetic to me that the same document that taught me how to make a wildly dangerous IRC bot in my teenage room for the lulz also re-taught me the stuff I needed to deliver a low-latency ML offloading demo at my serious(-ish) job 20 years later. Gave me a real warm fuzzy feeling :-)

My experience with CTCP flooding large channels channels and causing netsplits in my youth provided a perfect base of understanding for when my production servers started flooding status updates to each other and couldn't stay connected.

PS sorry, undernet admins and users. Also, thanks to the admin on #quebec who asked me to flood his channel so he could tune his bot to block flooders.

I have special warm feelings for Beej's guide.

I remember particularly enjoying the warm and jovial tone in his guide.

I first read through it some 20 years ago while being a student in an easter-european university, where the tone and style of professors was very "dictatorial", dry, and overly-technical.

Beej's style of exposure was a breath of fresh air, and brought a major realisation for the then young-me, that you can teach complex topics in a friendly manner.

> while being a student in an easter-european university, where the tone and style of professors was very "dictatorial"

I know it's just I typo, but now I have an image stuck in my head of a large rabbit, dressed up like Mussolini, lecturing about computer science.

Beej's guide was so amazingly helpful and welcoming when I found it over a decade ago.

Poorly written guides that try to be friendly or conversational are often worse than dry and terse guides of similar caliber, which really makes me appreciate the good and truly great ones.

And Beej's Guide is a truly great one.

I attempted to write something for more advanced audience. Not sure if it's a successful attempt though...

https://idea.popcount.org/2019-11-06-creating-sockets/

https://idea.popcount.org/2019-12-06-addressing/

If I remember correctly this network programming tutorial has been around for more than 20 years now, how times flies!

If you want a cross platform network programming guide in C, Lewis Van Winkle has written an excellent reference book[1].

[1]https://www.amazon.com/Hands-Network-Programming-programming...

If that book is as good as you say, it's a pity he published with Packt. Their stuff is typically very bad.

Agreed. I published a video course through Packt and the whole experience was absolutely awful.

I began writing a book for them in 2010 and quit when the goalposts kept being moved and had a different point of contact every week. Absolutely terrible experience.

Similar experience. In my case, they wanted a video course on a library that wasn't finalized or published, and was still in an obvious beta with frequent breaking changes. On top of that, I was in a 12hr timezone difference, and only wanted to communicate with me regularly at 11/12 at night on week days, which didn't work well. Oh, and they only wanted to use skype, an app I never use normally. I was promised promo codes and release on multiple websites, and I got a single weekend promo code, and only published on two websites. And the icing on the cake is now 100% of the people I worked with don't work at Packt any more, so I don't even have a person I can contact any more to work on promotions or updates.

Production failures due to bugs in both TCP-based servers and clients happen all the time, long time ago I invested a little time to learn basic socket programming in C and the ROI on this has really been spectacular. "Unix Network Programming" by Stevens is a great book on this topic, in particular it carefully discusses all the different ways things can go wrong. Wish there was something more up to date that could be recommended, but I don't know anything of comparable quality, so I think you still have to read it and later work out all the Linux-specific details, more modern APIs like epoll etc.

To anyone writing tutorials or guides, this is the gold standard - at least for me. After many years I still remember writing my first tcp client following this tut. I wish more content would be as focused and concise as this.

One if the best guides/books on programming I've ever read. This taught me the foundations of network programming and the fact it's available for free is incredible. I just took a second and ordered the paperback right now because of how fantastic it is.

Aside from the book being really in-depth and understandable, Beej adds in quite a bit of humor and that is something I love in a good software book.

Strangely no mention of High Performance Browser Networking https://hpbn.co

I also would mention Distributed systems for fun and profit http://book.mixu.net/distsys/ while being not exactly about network programming, it is likely a next step for anyone who's building apps that is scattered across several backends/services connected by the network

Beej's is the classic of classics.

I had the privilege of working with Beej for a couple years at my last job. He was one of my favorite coworkers I've ever had. Just great to be around and work with. Incredibly sharp, but also humble, easygoing, and eager to just solve problems.

The feeling is mutual!

It sounds like Beej needs to write a "Beej's Guide to Writing Guides".

This "Beej" fellow is a legend. This is an example of very clear documentation that scales well with your level. When I was learning C/C++ as a teenager, I found the guides to be very accessible. They were recommended all the time to people asking questions on cprogramming.com forums. As I've referred back to them as a professional I still find them comprehensive and helpful. This is an excellent model and level of quality for other technical writers to aim for.

Brian Hall: thank you!

This one and "Programming from the gound up" [https://download-mirror.savannah.gnu.org/releases/pgubook/Pr...] are the two bibles i used and often go back to.

Beej is a Lambda School instructor. He taught me CS.

Wait... the Lambda School that's constantly on HN for its disgruntled students, questionable success rates, and murky financials? What possessed beej to associate his name with them?

The view from the inside is different than the view from the outside.

Sure, here's an HN thread with lots of views from the inside: "Lambda School is the biggest mistake I made this year"[1]

[1] https://news.ycombinator.com/item?id=25415017

And here's some reporting that aggregates questionable practices and student complaints: "The High Cost of a Free Coding Bootcamp"[1]

And here's some paywalled reporting from The Information with even more student complaints: "Lambda School's Growing Pains: Big Buzz, Student Complaints"[2]

Please, tell me more about the view from the inside.

[1] https://www.theverge.com/2020/2/11/21131848/lambda-school-co...

[2] https://www.theinformation.com/articles/lambda-schools-growi...

A couple of decades ago, I spent a few years teaching an introduction to network programming using C on an embedded board running uCLinux for Network Engineering students. While my primary text was Stevens, Beej's guides were an invaluable secondary reference for my students. There were many, many occasions where students who were were having difficulty understanding my explanations could recover using Beej's approachable, application-oriented notes. Eventually, I found myself frequently abandoning my own notes and just lecturing from Beej's work. I miss the days when I still worked with students that close to the metal, helping them build their own network devices. Thanks for the reminder of a time I still have fond memories of.

Beej's guide got me through my networking class in college. As a result I actually understand networking. Thank you Beej!

I love this guide!

My first job out of university reqiured networking a small Linux device to an FPGA running a UDP stack, with nothing else. I'd never done anything with networking in C before, and this guide just made everything click

Would be interesting to see a Go or Rust version not it.

This guide saved my butt in school when I suddenly had to do C network programming with no relevant experience.

I share the same experience as I am currently taking CS6200 at Georgia Tech.

Haha, that was the exact class where I used it! Loved that class, though. By far my favorite in their MS program. It awakened a love for operating systems (and the general applicability of the concepts). AOS was also good and made me appreciate the point of cloud computing more.

Can confirm this is a nice introduction to network programming; it's how I got started. Once you know the basics you can switch to the man pages for more details.

Such simple, but informative guides should be how official documentations should be written.

Glad to see this is being updated. I have used Beej's Guide to learn network programming back in 2013 or 2014, and it was such a great resource.

Despite of its age, Beej's Guide is still one of the best introductions to network programming I've seen so far. I love how apart from the basic and concise explanation of TCP and UDP (and generally sockets in UNIX-like environments), there's also a separate, short "Advanced Techniques" section that can be very useful if you want to explore the subject even further.

I printed this from an internet cafe long back when I didn't have internet at home in India. I wanted to learn about sockets however I could.

I read this for the first time probably 15 years ago, and to this day I can't think about IPv6 without thinking about this passage from the guide:

  What does this suggest to you?

  That we need a lot more addresses. That we need not just twice as many addresses, 
  not a billion times as many, not a thousand trillion times as many, but 79 MILLION
  BILLION TRILLION times as many possible addresses! That’ll show ’em!

  You’re saying, “Beej, is that true? I have every reason to disbelieve large numbers.”
  Well, the difference between 32 bits and 128 bits might not sound like a lot; it’s
  only 96 more bits, right? But remember, we’re talking powers here: 32 bits represents
  some 4 billion numbers (232), while 128 bits represents about 340 trillion trillion
  trillion numbers (for real, 2128). That’s like a million IPv4 Internets for every
  single star in the Universe.

Pretty much learned c via this back in the day. It feels like it was in the 90s, but might have been early 2000s

edit: it was the 90s

“Some of you might want to do things the Pure Windows Way. That’s very gutsy of you, and this is what you have to do: run out and get Unix immediately!”

He's just joking of course. At first glance this seems like a great read. And he's funny too! :)

I do wonder how much of this is applicable to Rust though.

"At first glance this seems like a great read" Agree!

Sadly the Windows asynchronous (or something, I never quite got it) networking API seems very powerful. But I never found a comprehensible manual/tutorial for it.

Dr.Dobbs has had at least 2 articles on it.

https://www.drdobbs.com/open-source/io-multiplexing-scalable... (Also covers select and /dev/poll but lacks epoll,kqueue)

https://www.drdobbs.com/cpp/multithreaded-asynchronous-io-io...

I remember chatting in the fringes when nodeJS was doing their proper win32 porting and they did have some issues getting things stable due to lack of documentation but iirc got some help from MS so the libuv code should be usable as a reference for behaviours (As well as being fairly battle tested by now).

https://github.com/libuv/libuv/tree/v1.x/src/win

I’ve been trying to figure out the entire windows networking stack recently, particularly some more obscure parts and the docs have been pretty bad unfortunately. A lot of the higher level stuff fees really superficial and the lower level stuff it’s it own mess (all sorts of broken links and links to outdated versions in the NDIS docs).

oh hey, I'm actively reworking through this guide for the 3rd time. I always manage to get rusty in the fundamentals after enough time not practicing.

the latest variant is highly digestible. the struct walkthrus seem more accessible

I remember many years ago learning how to use select() with this guide and then use it to speed up some scanning tool I had found on the internet.

It felt incredible that _I_ could do that as someone who had just started programming.

Thank you Beej.

A couple of observations regarding select(): its use is not limited to sockets; and, quoting Wikipedia, "with the c10k problem, both select and poll have been superseded by the likes of kqueue, epoll, /dev/poll and I/O completion ports."

And now io_uring too.

Georgia Tech's Graduate Introduction to Operating systems OMSCS class rings a bell. Socket programming was fun in that class. And by fun I mean hours of hair pulling while debugging.

Was OMSCS worth it?

My latest immersion into Beej's guide was through the GIOS course too! It also opened my eyes to the amount of familiarity/expertise my older co-workers had with systems programming (they helped me when when they heard me whining about the socket programming assignment). It taught me not to dismiss someone just because they don't know the latest TensorFlow API/Neurips paper.

Beej has had great guides for many things on the internet for decades. I fondly remember learning C from Beej's guide to C [1] upon being recommended by WinterMute (from the Nintendo homebrewing community). Best introduction to programming I've seen by far!

[1]: https://beej.us/guide/bgc/

What a classic! Back in 1999 I wrote the networking infrastructure for a distributed, evolutionary, fractal art system for Steven Rooke (maybe you remember the fractal absolut vodka bottle on the back of Wired magazine) and I learned everything from Beej's guide. This brought back great memories. What a serious internet classic for so many software devs. Thanks Beej!

Beej's guide is great and still very relevant today (at least if you're programming in C). Are there any equivalent documentation/tutorials for other domains? An equivalent for machine learning would be great, although part of what makes Beej's guide timeless is that a lot of the underlying concepts and syscalls have been static for decades.

I've always loved networking and recently implemented an IP stack just for fun. It doesn't take that long to be able to write ping yourself and ping Internet hosts. I was going to go as far as TCP but haven't gone there yet.

I think it's now time to read this and find out all the stuff I got wrong and cement the stuff I got right.

I recently wrote a good enough tcp to layer an http server on top. It's not very good, but I did it, and now I can use someone else's ;)

PS Hello fellow toast

Hello :)

I'll definitely finish mine one day then. I was more interested in the IP layer when I did mine and learning about routing. TCP seemed a bit too complicated and not that interesting, but it would be cool to have at least once gone from a raw socket to HTTP.

I know exactly what you mean as well. When using technology there is a comfort in knowing that you could conceivably implement it yourself if you absolutely had to.

Networking is probably one of the parts of computers I’ve been consistently interested in over the years. I was recently looking at the man page for the addresss_families supported and there’s all sorts of crazy stuff that’s been adapted to the socket API in there.

I’ve been working on developing myself a custom ISDN stack recently. So far it’s just been me trying to design it at a high level without falling to feature creep.

I think what I love about it is the Internet is the biggest machine in the world! I can literally flip bits on the other side of the world by pressing some of these buttons here on my desk. After becoming pretty much accustomed to living behind an IPv4 NAT my interest was rekindled when my ISP deployed IPv6 and all of a sudden each device in my house has a real public IP address.

Good for getting started with network programming. My university refers this for the computer networks lab course.

I read your guide when i was 14 (translated to hebrew), until now, i have managed to write a functional usermode tcp/ipv4 stack, and now in the middle of development of a usermode-based wireless networking device in an international company. You are a big part of it. Thanks.

> s/he

Just use they, it reads better and includes everyone instead of people with binary genders

Agreed.

I've been retraining myself to default to singular they. https://en.wikipedia.org/wiki/Singular_they

Old dog, new tricks. But I'm slowly adapting.

I've also personally never understood the slash syntax. Since one word requires the "s" and the other doesn't, shouldn't we use parentheses like when words may or may not be plural? e.g. "(s)he" like you might say "socket(s)" or "Unix(es)"?

Moot point if it doesn't solve the issue of it still being binary, I guess.

Ironically, with “they” becoming a more common specific-individual-identity-pronoun preference, it is at risk of losing its inclusivity, and of becoming as problematic for unknown individual preference as she and he.

But that's a problem for the future, right now “they” is usually the best inclusive pronoun available.

Beej thank you! Like so many others your work was a beacon for me early on and the best resource in the world to explore writing networking code.

Cannot wait to see what you publish next, so glad you’ve decided to publish even more!

How do you handle servers, which need to be accessible by desktop, mobile and web application?

Can I use those low level API's or do you know some server/client libraries which simplify this for UDP and TCP channels?

Your question is insufficiently specific ... it could mean nearly anything. You need to be clearer about what equipment you have, and what you're trying to accomplish.

As it stands, I don't think anyone can answer except it a completely generic way:

Almost every system has libraries to help, but it depends on what you're running on, what you're running over, and what you're trying to do.

That is covered[1], though it is outdated if you want it to be able to handle as many connections as possible in a fast way.

There are also thousands of higher-level libraries that would let you avoid having to deal with these lower-level APIs directly.

[1] https://beej.us/guide/bgnet/html/#poll

If you're serving webpages, look for a networking library that handles HTTP.

If you're sending arbitrary chunks of data (like for a game), use a socket library. I've used WebSockets in the past, which handles the low-level stuff under the hood. There are libraries that implement it for Java, Go, C++, JS, etc. Check it out at https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_...

It's not totally headache-free though - some issues I ran into were:

- running locally vs over the internet

- data formatting

- recovering from timeouts/dropped connections

After reading Beej Guide I think I find "The Linux Programming Interface" a good book in general to learn about sockets and other linuxy thing etc. Sadly it hasn't been updated since 2010.

Oh wow, thank you Beej for this work and content! Your resource has been a tremendous reference to many of us myself included and still stands as one of the best resources to network programming today!

This site has become groundhog day, should just automate re-submission: https://hn.algolia.com/?q=beej

When I TA'ed a course that taught networking fundamentals, I always pointed folks at this guide when they were struggling with assignments. Can't believe that was 8 years ago.

I credit beej to my first serious job. I worked through the network and concurrency guides and landed the job that started me off on my career. Thanks Beej! Please keep it up :D

Among other things, Beej has been a leader in putting together events and connecting software people here in Bend, Oregon. Well, when getting together was a thing, at least.

As soon as I read the title, I felt joy! I had followed this guide when I had began programming early on and had a great experience. I recognize it by its name alone!

I’ve always felt like the hard part of networking isn’t the APIs but the threading problems that you will have very soon after you try to write anything serious.

Currently taking Graduate Introduction to Operating Systems at Georgia Tech, and this guide has been like a bible for me. Huge thanks to Beej!

Good guide to socket programming. Does it cover sctp? And more importantly is sctp support part of Kernel/glibc presently?

https://www.google.com/search?q=site%3Abeej.us+sctp

> Your search - site:beej.us sctp - did not match any documents.

In contrast:

https://www.google.com/search?q=site%3Abeej.us+udp

> About 9 results (0.25 seconds)

So I'd guess that the guide doesn't cover sctp.

========

Then:

https://duckduckgo.com/?q=is+sctp+support+part+of+Kernel%2Fg...

Returns:

> https://www.kernel.org/doc/html/latest/security/SCTP.html

(and more ...)

That discussion of merging sctp functionality into glibc is from 2004. Anyone knows what happened after that?

sctp only be came widely available after websockets and I think due to data channel implementations in WebRTC.

I remember reading this when I was in high school out of curiosity. Thanks again for writing this (and many more), Beej.

I think this thing has been around for at least 15 years. Glad to see its still being maintained and updated.

At Northeastern we use this guide as the canonical “textbook” for the graduate distributed systems course.

download as pdf https://buzon.io/downloads/75e686f94e1d4a599f2ee9ad521123865...

Or you can get it from the official source [0] and not some PDF on a file sharing site linked from an HN comment.

[0] https://beej.us/guide/bgnet/

Wonderful resource, really helped me have fun playing with C sockets. Thank you Beej!

in case somebody is interested in offline version, there are pdf versions as well https://beej.us/guide/bgnet/

This was my first intro to network programming in school very very long time.

This is so useful I can't believe I have never seen it before.

Be sure to check out Beej's other guides. They're some of the most useful I've seen.

Wow I read this in 2006ish. Amazing document to still be around.

This is gold! Thank you so much.

great classic !! I didn't know it was still maintained, thanks beej !

beej's guides are the best

465

https://beej.us/guide/bgipc/html/multi/index.html is also good

Title should mention it's about linux.

Well, anything that'll run gcc. He does include a section for Windows programming for the brave -

- https://beej.us/guide/bgnet/html/#windows

It's useful for any Unix that has BSD sockets, not just Linux.

Even though some of the API specifics change, the BSD sockets API has been widely copied. It's a pretty decent introduction to the concepts in general.

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