ciaranjodonnell

ciaranjodonnell

Release It! Second Edition: Wrong number of TCP Connections (page 55)

The description of the limits of TCP connections on your server is kind of wrong.
The book says:

If you look at the TCP packet format, you’ll see that a port number is 16 bits long. It can only go up to 65535. Different OSs use different port ranges for ephemeral sockets, but the IANA recommended range is 49152 to 65535. That gives your server the ability to have at most 16,383 connections open. But your machine is probably dedicated to your service rather than handling, say, user logins. So we can stretch that range to ports 1024–65535, for a maximum of 64,511 connections.
Now I’ll tell you that some servers are handling more than a million concurrent
connections. Some people are pushing toward ten million connections on a
single machine.
If there are only 64,511 ports available for connections, how can a server have a million connections? The secret is virtual IP addresses. The operating system binds additional IP addresses to the same network interface. Each IP address has its own range of port numbers, so we would need a total of 16 IP addresses to handle that many connections.

This TCP information is sort of correct, but the implication is wrong. Those limits apply to the number of server processes that can LISTEN for connections. However those processes can accept lots of connections from different source IP Address/Port combinations. So a single process could handle thousands of connections on a single port. This is how all web servers work. The server listens on port 80, and accepts a request from my IP address with port like 43567. While processing my request it can also accept another connection from YOUR IP Address with whatever port number your web browser connected out from.

So having LOTs of listening processes might need virtual IP addresses, but having a single application accept lots of connections only needs one IP Address and one listening port.

Where Next?

Popular Pragmatic Bookshelf topics Top

abtin
page 20: … protoc command… I had to additionally run the following go get commands in order to be able to compile protobuf code using go...
New
jimmykiang
This test is broken right out of the box… — FAIL: TestAgent (7.82s) agent_test.go:77: Error Trace: agent_test.go:77 agent_test.go:...
New
AleksandrKudashkin
On the page xv there is an instruction to run bin/setup from the main folder. I downloaded the source code today (12/03/21) and can’t see...
New
brian-m-ops
#book-python-testing-with-pytest-second-edition Hi. Thanks for writing the book. I am just learning so this might just of been an issue ...
New
jskubick
I think I might have found a problem involving SwitchCompat, thumbTint, and trackTint. As entered, the SwitchCompat changes color to hol...
New
taguniversalmachine
It seems the second code snippet is missing the code to set the current_user: current_user: Accounts.get_user_by_session_token(session["...
New
mert
AWDWR 7, page 152, page 153: Hello everyone, I’m a little bit lost on the hotwire part. I didn’t fully understand it. On page 152 @rub...
New
EdBorn
Title: Agile Web Development with Rails 7: (page 70) I am running windows 11 pro with rails 7.0.3 and ruby 3.1.2p20 (2022-04-12 revision...
New
Keton
When running the program in chapter 8, “Implementing Combat”, the printout Health before attack was never printed so I assumed something ...
New
redconfetti
Docker-Machine became part of the Docker Toolbox, which was deprecated in 2020, long after Docker Desktop supported Docker Engine nativel...
New

Other popular topics Top

Devtalk
Reading something? Working on something? Planning something? Changing jobs even!? If you’re up for sharing, please let us know what you’...
1031 17377 381
New
ohm
Which, if any, games do you play? On what platform? I just bought (and completed) Minecraft Dungeons for my Nintendo Switch. Other than ...
New
Exadra37
Please tell us what is your preferred monitor setup for programming(not gaming) and why you have chosen it. Does your monitor have eye p...
New
Rainer
My first contact with Erlang was about 2 years ago when I used RabbitMQ, which is written in Erlang, for my job. This made me curious and...
New
AstonJ
In case anyone else is wondering why Ruby 3 doesn’t show when you do asdf list-all ruby :man_facepalming: do this first: asdf plugin-upd...
New
mafinar
Crystal recently reached version 1. I had been following it for awhile but never got to really learn it. Most languages I picked up out o...
New
wmnnd
Here’s the story how one of the world’s first production deployments of LiveView came to be - and how trying to improve it almost caused ...
New
PragmaticBookshelf
Rails 7 completely redefines what it means to produce fantastic user experiences and provides a way to achieve all the benefits of single...
New
PragmaticBookshelf
Author Spotlight Jamis Buck @jamis This month, we have the pleasure of spotlighting author Jamis Buck, who has written Mazes for Prog...
New
AstonJ
This is a very quick guide, you just need to: Download LM Studio: https://lmstudio.ai/ Click on search Type DeepSeek, then select the o...
New

Sub Categories: