Client-server architecture in Unity - Step-by-Step Execution

Concept Flow - Client-server architecture

Client sends request

↓

Server receives request

↓

Server processes request

↓

Server sends response

↓

Client receives response

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Client uses data

The client sends a request to the server, the server processes it and sends back a response, which the client then uses.

Execution Sample

Unity

using UnityEngine;
using System.Net.Sockets;

// Client sends message to server
TcpClient client = new TcpClient("127.0.0.1", 5500);
NetworkStream stream = client.GetStream();
byte[] data = System.Text.Encoding.ASCII.GetBytes("Hello Server");
stream.Write(data, 0, data.Length);

// Remember to close the stream and client after use
stream.Close();
client.Close();

This code shows a Unity client connecting to a server and sending a message.

Execution Table

Step	Action	Details	Result
1	Client creates TcpClient	Connects to 127.0.0.1:5500	Connection established
2	Client gets NetworkStream	Prepares to send data	Stream ready
3	Client encodes message	"Hello Server" to bytes	Byte array created
4	Client writes to stream	Sends bytes to server	Message sent
5	Server receives message	Reads bytes from stream	Message received
6	Server processes message	Interprets "Hello Server"	Ready to respond
7	Server sends response	Sends reply bytes	Response sent
8	Client reads response	Reads from stream	Response received
9	Client uses response	Displays or processes data	Interaction complete
10	Connection closed	Client or server closes connection	Communication ended

💡 Communication ends after client and server exchange messages and close connection.

Variable Tracker

Variable	Start	After Step 1	After Step 4	After Step 8	Final
client	null	TcpClient connected	TcpClient connected	TcpClient connected	Closed or disposed
stream	null	NetworkStream ready	NetworkStream ready	NetworkStream ready	Closed
data	null	null	Byte array with message	null	null
response	null	null	null	Byte array with server reply	Used or stored

Key Moments - 3 Insights

Why do we convert the message string to bytes before sending?

Network communication sends bytes, not strings. See execution_table step 3 where the string is encoded to bytes before sending.

What happens if the server is not running when the client tries to connect?

The client cannot establish a connection (step 1 fails). This stops communication early, so no stream or data is sent.

Why do we need to close the connection after communication?

To free resources and avoid hanging connections. See execution_table step 10 where connection is closed to end communication.

Visual Quiz - 3 Questions

Look at the execution_table, what is the state of 'client' after step 1?

A Connection closed

B TcpClient connected

C null

D Byte array created

💡 Hint

Check variable_tracker row for 'client' after Step 1.

At which step does the client send the message bytes to the server?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look at execution_table action descriptions for sending data.

If the client never closes the connection, what happens according to the flow?

A Resources remain used, connection hangs

B Server closes connection automatically

C Communication ends normally

D Client reconnects automatically

💡 Hint

Refer to key_moments about closing connection and execution_table step 10.

Concept Snapshot

Client-server architecture:
- Client sends requests to server
- Server processes and replies
- Communication uses network streams
- Messages sent as bytes
- Connections must be closed after use

Full Transcript

Client-server architecture means one program (client) asks another (server) for data or service. The client opens a connection to the server's address and port. It sends a message by converting text to bytes and writing to the network stream. The server reads the bytes, processes the request, and sends back a response. The client reads the response bytes and uses the data. Finally, both close the connection to free resources. This flow ensures clear communication between two programs over a network.