🧠 C# .NET Remote Socket Messaging App

A real-time, cross-device remote messaging system developed using C#, .NET Framework, and raw TCP sockets — built entirely without socket.io or any third-party messaging protocols. The application is divided into two parts: a WPF-based client and a console-based TCP server, and demonstrates the implementation of a custom communication protocol, asynchronous networking via NetworkStream, and stream-based image transfer. Communication occurs through structured, delimited message packets, enabling both text and compressed screenshot delivery between remote devices over TCP.

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🎯 Objective

This project was built to:

• Understand and implement low-level socket communication in .NET
• Gain hands-on experience with WPF client development
• Learn how to design and parse custom message packet protocols
• Build real-time client-server communication across remote machines

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🔐 Notes & Considerations

• Pure socket implementation: no external libraries like SignalR, socket.io, etc.
• Image data is sent as Base64 string inside packet
• No message persistence — communication is live-only
• LAN or WAN compatible (requires port forwarding on host if over public internet)

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💡 Key Highlights

Area	Implementation
Protocol Design	Custom delimited message packets over raw NetworkStream
Asynchronous Networking	TcpListener, TcpClient, Stream.ReadAsync/WriteAsync
UI/UX	Built with WPF, dynamic textbox/image rendering, async-safe UI updates
Remote Communication	Clients connect from different machines using IP/Port over LAN/WAN
Screenshot Transfer	Compressed via JPEG, streamed as Base64
Data Routing	Server routes packets via ConcurrentDictionary<string, TcpClient>
Error Handling	Robust detection for malformed packets, invalid base64, disconnected clients

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🧪 Technical Overview

🔌 Message Packet Structure

Each communication is encapsulated in a simple, custom message packet, manually constructed and transmitted via TCP:

senderId:recipientId:payload

• payload can be a UTF-8 text message or a Base64-encoded image.

📝 Examples

• alice:bob:Hello from my laptop!
• alice:bob:data:image/png;base64,iVBORw0K...

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🧠 Server Architecture

• Listens for TCP clients using TcpListener
• Accepts first incoming string as the userId
• Maps users in memory via thread-safe dictionary:

  ConcurrentDictionary<string, TcpClient> _clients;

• Parses message packets and forwards to recipients
• Logs connection status and errors to console

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🖥️ Client Features

• Built with WPF (XAML + C#)
• UI for entering:
  • User ID
  • Server IP and Port
  • Recipient ID and message
• Supports:
  • Sending text messages
  • Capturing & sending full-screen images
• Live preview of received image messages via BitmapImage stream binding

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📷 Streamed Screenshot Flow

1. Capture screen using:

   Graphics.CopyFromScreen(...)

2. Compress to JPEG in memory:

   resizedBitmap.Save(MemoryStream, jpegCodec, encoderParams);

3. Convert to Base64 string and embed in message packet:

   $"sender|recipient|data:image/png;base64,{Convert.ToBase64String(bytes)}"

4. Send over NetworkStream.WriteAsync(...)

5. Receiver decodes stream and updates WPF UI image preview

✅ All without saving temporary files — the entire process is stream-based.

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🖼️ Architecture

SocketMessagingApp/
├── SocketClientWpf/         # WPF-based UI client
│   ├── MainWindow.xaml(.cs) # UI, messaging, screenshot logic
│   ├── Client.cs            # Simple async TCP client
│   └── App.xaml / AssemblyInfo.cs
│
└── SocketServerHost/        # Console-based TCP server
    └── Program.cs           # Client manager, message router

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🚀 How to Run

🖥️ 1. Start Server

cd SocketServerHost
dotnet run

Enter IP and port to listen on:

Sunucu IP adresini girin: 0.0.0.0
Port numarasını girin: 5000

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💻 2. Start WPF Client

• Open SocketClientWpf in Visual Studio
• Run the app
• Fill in:
  • Your User ID
  • Server IP and Port
  • Recipient ID
  • Optional message or screenshot trigger

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📸 Demo

a real-time TCP-based communication between two clients, featuring both text messaging and live screenshot sharing via memory stream and base64 encoding.

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🌐 Running the Application: Local & Remote Scenarios

This application can be tested on the same machine or across different machines on the same network (LAN).

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💻 Local Test on the Same PC

To simulate a full client-server flow without multiple devices:

• Run the server in one terminal or console window
• Run the client (WPF) separately
• This mimics a real network connection over TCP, even on the same device

✅ Messages will still pass through the OS’s TCP stack and be handled via NetworkStream.

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🌐 Remote Test from Another PC on LAN

You can also run the server and client on two different machines in the same Wi-Fi or LAN network.

✅ Server Setup

• Launch the server and enter 0.0.0.0 as the IP address
  → This binds the server to all network interfaces
• Choose a port (e.g., 5000)
• Ensure the firewall allows incoming connections:

New-NetFirewallRule -DisplayName "SocketServer" -Direction Inbound -Protocol TCP -LocalPort 5000 -Action Allow

✅ Client Setup (on another PC)

• Launch the WPF client
• Connect using:
  • The actual local IP address of the server machine (e.g., 192.168.x.x)
  • The same port used by the server

✅ Once connected, full communication is established:

• 🔹 Text messages
• 🔹 Screenshots (streamed as JPEG-compressed base64)

📌 Avoid using localhost on the client — always use the server’s real IP address.

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🧪 In both setups, communication is handled entirely via raw TCP sockets using .NET NetworkStream, with no middleware, no third-party messaging library, and no simulation — this is real asynchronous socket programming in action.

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📄 License

MIT License

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👩‍💻 Author

Developed by rukiyeberna
A networking-focused project demonstrating end-to-end socket communication, protocol design, and real-time stream handling in C#.