BaSzErr - blog:2020:04:03

2020-04-03_-_cross-compiling_in_golang

anonymous@undisclosed.example.com (Anonymous) — Tue, 15 Jun 2021 20:09:29 +0000

2020-04-03 - cross-compiling in golang

i'm recently working on one project in Go. this is my first above-hello-world level project in this language. there is a chance it will be open source one day, but for now let's just call it “a project”. i plan to write a separate post on my impressions on the language, but one thing that was a huge positive surprise for me is cross compiling.

let's take a simple Go program:

package main
import "fmt"
func main() {
    fmt.Println("hello, world!")
}

and compile it:

go build

now let's cross-compile it for Raspberry Pi:

GOOS=linux GOARCH=arm GOARM=5 go build

after nearly 2 decades of C/C++ for both regular and embedded systems, my first though here was: son of a bitch – they can do this…

2020-04-03_-_out_of_ipv4

anonymous@undisclosed.example.com (Anonymous) — Tue, 15 Jun 2021 20:09:30 +0000

2020-04-03 - out of IPv4

not exactly a news, but around the end of 2019 Europe ran out of IPv4 addresses. will there be any new ones? yes, if some1 will give address (pool) back, which is not likely to happen anywhere soon.

i've heard about shortages of IPv4 addresses and predicted issues related to it, and a need to move to IPv6 since about 20 years now. maybe it's finally time to do so…

2020-04-03_-_reserving_non-privileged_ports_on_linux

anonymous@undisclosed.example.com (Anonymous) — Tue, 15 Jun 2021 20:09:29 +0000

2020-04-03 - reserving non-privileged ports on linux

using TCP/UDP ports < 1024 is reserved for root. OS will never auto-assign it to anything (eg. random source port when creating new TCP connection). these are however reserved for root user and are also typically already allocated for standard services, you do not wish to be confused with.

so normally you use port numbers above 1024. there is a catch, though – in that range, kernel will auto-assign ports as well. while most of the time you're going to be just fine, there is a small chance you'll be out of luck and will try to use port, that is already in use by some other, random client, outside of your jurisdiction.

it turns out there is a solution for that – you can reserve port range or particular ports for these purposes! :)

$ cat /proc/sys/net/ipv4/ip_local_port_range
32768	60999

$ cat /proc/sys/net/ipv4/ip_local_reserved_ports
4242,5151

by writing to these files (or doing proper sysctl) you can control which ports are to be used by kernel for auto-assigning (ip_local_port_range) and which ports are reserved and should never be used for these purposes (ip_local_reserved_ports). the setting is redundant, it is a bit easier to manage, as auto-assign port range can overlap with reserved ports, thus you effectively “remove” some ports from the pool.

2020-04-03_-_vr_games

anonymous@undisclosed.example.com (Anonymous) — Tue, 15 Jun 2021 20:09:30 +0000

2020-04-03 - VR games

recently a friend of mine bought Oculus VR. i had a chance to play with it briefly. i must say i'm impresses with the progress in the area. last time i had VR headset on (around 2014) graphics looked terrible and fun was… well there was not much fun out of it. things have progressed a lot since then. yes, the field of view is still fairly limited, but still – this time i was impressed.

games have also progressed. half-life: alyx was recently released¹⁾ – the best match for VR i have ever seen/heard of. with half-life's physics engine, this makes a great match for VR. what is limited and (judging from game play recordings – i have not had a chance to play myself) kinda awkward is moving around. obviously with VR googles on, you cannot move around a lot, as your room is limited in size. ;) in “alyx” it is solved so that you point where you want to move, and just “jump in there”. so forget about classic movements like going backwards while firing at the enemy or strife-and-shoot trick. maybe i'm just a creature of habit, but i guess i'd miss that a lot…

so VR is best when you can sit (or at least stand still) and just move head/arms around. i am still wondering why there is no flight simulator for that platform? you sit (in the cockpit) and move rudders/throttle (and fire, if this would be a fighter(jet)). sounds like a perfect match! moving head around is very important there and really awkward with keyboard and/or mouse – VR would solve this making it a really realistic experience!

¹⁾

too bad there is no non-VR version!