How PCs and smartphones communicate

When you open a website, send a message, or watch a video on a PC or smartphone, the device performs processing for communication internally.

From a human point of view, communication looks very simple.

Open a URL in a browser. Search. Send a message. Upload an image. Play a video.

But in reality, an app is not communicating outward all by itself.

Communication works through cooperation among the app, the OS, the device's network functions, Wi-Fi routers, cell towers, and similar parts.

This article explains how communication starts inside a PC or smartphone and how it is sent to outside networks.

Detailed mechanisms such as IP addresses, DNS, HTTP/HTTPS, TCP/UDP, and communication logs are covered in other articles.

How do PCs and smartphones start communication?

Communication often starts with an action in an app.

For example, consider opening a website in a browser.

When you click a search result or enter a URL, the browser creates a request: "I want to open this website."

It is the same when you send text in a messaging app.

When you enter text and press the send button, the app creates a request: "I want to send this message."

When uploading an image, the app prepares data to send: "I want to send this image data."

When watching a video in a video app, the app prepares a request: "I want to receive this video data."

In other words, the first trigger for communication is that the app creates "what it wants to exchange with the outside."

However, the app does not directly communicate with servers around the world as-is.

The request or data prepared by the app is passed to the OS.

Apps create the content they want to communicate

Apps include browsers, messaging apps, social media apps, video apps, map apps, game apps, and similar software.

These apps communicate externally as needed.

Browsers communicate to retrieve web pages.

Messaging apps communicate to send and receive text, images, audio, files, and similar data.

Map apps communicate to obtain map data and route information.

Video apps communicate to receive video data.

In this way, an app creates the content of the communication: "what it wants to send" or "what it wants to receive."

But the app alone does not complete the communication.

The app asks the OS, "Please send this communication outside."

The important point here is that communication is not the action of an app alone. It uses the mechanism of the whole device.

The OS has the role of sending communication outward

The OS is the basic software that manages the whole PC or smartphone.

On PCs, examples include Windows, macOS, and Linux.

On smartphones, examples include Android and iOS.

The OS manages app startup, file management, screen display, keyboard and touch operations, security, network functions, and more.

Communication is also one of the important functions managed by the OS.

When an app creates something it wants to send or receive, the OS receives that communication request.

It then decides which network function should be used to send it outward.

For example, if the device is connected to Wi-Fi, the OS sends communication outward through Wi-Fi.

If a smartphone is using a mobile connection, the OS uses the mobile communication function.

If a PC is connected with a LAN cable, it uses wired LAN.

Also, if a VPN is being used, the OS may process that communication so it passes through the VPN.

In this way, the OS receives communication requests from apps and uses the device's network functions to send them outward.

Communication is not "the app reaching outside on its own."

The flow is that the app prepares a request or data, the OS receives it, and the network function sends it externally.

Devices have functions for communication

PCs and smartphones contain functions for communicating with the outside.

On a PC, there may be a Wi-Fi adapter or a wired LAN port.

A Wi-Fi adapter is the part used to communicate with Wi-Fi radio signals.

A wired LAN port is a connector used to communicate through a LAN cable.

On a smartphone, there are Wi-Fi functions and mobile communication functions.

When using Wi-Fi, the smartphone communicates with a nearby Wi-Fi router.

When using mobile communication, the smartphone communicates with a nearby cell tower.

These communication functions allow PCs and smartphones to connect to external networks.

However, a PC or smartphone is not directly connected by itself to servers all over the world.

The device first sends communication to nearby network equipment.

On home Wi-Fi, it first sends communication to the Wi-Fi router.

On smartphone mobile communication, it first sends communication to a nearby cell tower.

On wired LAN, it sends communication through a LAN cable to a router or network device.

From there, the communication moves through the ISP/network operator's network and internet routes toward the destination.

Information is handled as 0 and 1 data

Now let us also look at how information is handled inside the device.

From a human point of view, information takes many forms.

Text. Images. Audio. Video. Files. App operations.

But computers do not understand these in the same form humans do.

Computers handle text, images, audio, and similar things as numeric data.

The basis of that is 0 and 1.

For example, the English letter "A" can be represented in a common character code as a sequence of 0s and 1s such as 01000001.

Even if humans see it as the letter "A," inside the computer it is handled as data with a defined numeric form.

Images are the same.

An image is data made from many pieces of color and brightness information.

Even if it looks like a photo or illustration on screen, inside the computer it is handled as a collection of numbers describing which color to show at which position.

Audio is the same.

Humans hear audio as sound.

But inside a computer, it is handled as a collection of numbers made by measuring sound waves in small pieces.

In other words, text, images, audio, and video are all handled as data inside the device, and their basis is a combination of 0 and 1.

0 and 1 are sent as signals

However, the numbers 0 and 1 themselves do not fly through the air or through cables as-is.

0 and 1 are a representation computers use to handle information.

In actual communication, 0 and 1 data is sent as electrical, optical, or radio signals.

In wired LAN, information is sent as electrical signals over a cable.

In optical fiber, information is sent as optical signals.

In Wi-Fi and mobile communication, information is sent as changes in radio signals.

In other words, data created inside the device is converted into physical signals when sent outward.

At that point, information corresponding to 0 and 1 is represented through things such as higher and lower electrical states, changes in light, or changes in radio waves.

Communication is not just pressing a button on screen.

It works because an app creates data, the OS processes it, the device's communication function converts it into signals, and those signals are sent to network equipment.

Why are 0 and 1 used?

One major reason computers use 0 and 1 is that machines can judge two states stably.

For a machine, distinguishing between two states is relatively easy.

For example, whether voltage is low or high.

Whether a signal is absent or present.

Whether something is below or above a certain threshold.

With two levels like this, machines can judge more stably.

If information were represented using many fine levels, such as 10 levels, a machine would need to distinguish small differences accurately.

But real communication has noise.

Electrical signals can become disturbed.

Radio signals can be affected by other radio signals.

When distance becomes longer, signals can become weaker.

In such environments, distinguishing two levels, 0 or 1, is more stable than distinguishing 10 fine levels.

Designing information as two states, 0 and 1, is easy for computers and communication equipment to handle, and it is easier to judge in real environments with noise.

That is why computers handle information as combinations of 0 and 1.

The device first sends communication to nearby equipment

When a PC or smartphone communicates, the device first sends communication to nearby network equipment.

When using Wi-Fi at home, school, or work, the PC or smartphone first communicates with a Wi-Fi router.

After that, communication moves from the Wi-Fi router to the ISP/network operator's network, then through internet routes toward the target server.

When using mobile communication on a smartphone, the smartphone first communicates with a nearby base station/cell tower.

After that, it passes through the mobile network operator's network and heads toward the destination on the internet.

When using wired LAN, communication is sent from the PC through a LAN cable to a router or network device.

This flow can be summarized as follows.

1. You operate an app
2. The app prepares what it wants to send or receive
3. The OS receives the communication request
4. The OS uses the device's network function to send it outward
5. Signals are sent through Wi-Fi, mobile communication, wired LAN, or similar methods
6. They first reach nearby equipment such as a Wi-Fi router or base station/cell tower
7. From there, they move to an external network

In this way, communication is not completed by the device alone.

Apps, the OS, the device's communication functions, routers, cell towers, ISP/network operator networks, and similar parts cooperate.

Communication is not decided by one part alone

As organized on this page, communication from PCs and smartphones is not decided by one part alone.

The app prepares what it wants to send or receive.

The OS receives that communication request and uses network functions to send it outward.

The device's communication function converts data into electrical, optical, radio, or similar signals.

Wi-Fi routers and cell towers connect those signals to external networks.

In this way, communication is built from multiple layers.

For that reason, when understanding how communication works, it is not enough to view it broadly as "the browser is communicating" or "the smartphone is communicating."

In reality, behind the scenes, the app, OS, device communication functions, and surrounding network equipment each have roles.

With this perspective, it becomes easier to understand IP addresses, DNS, HTTP/HTTPS, TCP/UDP, VPN, WebRTC, and similar topics later.

An important perspective for learning anonymity

When thinking about anonymity, many people focus on the browser.

Of course, the browser is important.

When viewing websites, the browser communicates externally.

Browser settings can also change what information is visible externally.

However, looking only at the browser is not enough.

Actual communication involves apps, the OS, network settings, Wi-Fi, mobile lines, DNS settings, VPN settings, and similar factors.

For example, even if you are careful about anonymity in the browser, another app may be communicating.

The OS itself may communicate for update checks, time synchronization, and similar purposes.

DNS settings also change where name-resolution queries are sent.

Even if you think you are using a VPN, if settings are insufficient, unintended communication may leave through the normal connection.

Also, browsers have functions such as WebRTC that, depending on settings, can lead to network information leaks.

In this way, thinking about anonymity requires looking not only at "the browser," but also at "how the whole device is communicating."

To understand browser settings, DNS settings, VPN settings, WebRTC leaks, and similar issues, it is important first to grasp where device communication starts and how it leaves the device.

Summary

Communication from PCs and smartphones starts with app operations.

Opening a website in a browser.

Sending text in a messaging app.

Uploading an image.

Watching a video.

When you do these actions, the app prepares what it wants to send or receive.

That request or data is passed to the OS.

The OS uses network functions such as Wi-Fi, wired LAN, and mobile communication to send it outward.

The device's communication function sends data as electrical, optical, radio, and similar signals.

Those signals first reach nearby equipment such as a Wi-Fi router or cell tower, and from there move to an external network.

Also, inside the device, information such as text, images, audio, and video is handled as numeric data.

The basis of that is 0 and 1.

0 and 1 are used as a foundation of computers and communication because machines can judge them stably and they are relatively resistant to noise.

The important point in this article is that communication is not "the app reaching outside on its own."

Communication works only through cooperation among the app, OS, device network functions, Wi-Fi router, cell tower, and similar parts.

This perspective is also important when learning about anonymity.

When thinking about anonymity, you need to look not only at the browser, but also at apps, the OS, network settings, Wi-Fi, mobile lines, DNS settings, VPN settings, and similar factors.

Understanding how communication starts inside a PC or smartphone and how it leaves the device is the foundation for understanding networks and anonymity.

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