Add [0] TCP Server & Client - Bash implementation - cchopin

.gitignore

@@ -129,4 +129,13 @@ venv.bak/
 dmypy.json
 
 # Pyre type checker
-.pyre/
+.pyre/
+
+# macOS
+.DS_Store
+.DS_Store?
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.db

Projects/0_bash_TCP_server/README.md

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+# [0] TCP Server & Client - Bash | cchopin
+
+A cross-platform TCP server and client implementation using bash and netcat for receiving and sending messages.
+
+## Project overview
+
+This project implements a basic TCP communication system with:
+- **Server**: Listens on port 7777 and receives messages
+- **Client**: Connects to server and sends messages
+- **Cross-platform support**: Linux, macOS, and Windows compatibility
+- **OS detection**: Automatic detection and adaptation to different operating systems
+
+## Learning objectives
+
+- Understanding TCP client-server communication
+- Cross-platform bash scripting
+- Process handling and OS detection
+- Network programming fundamentals
+- Basic security considerations in network applications
+
+## Architecture
+
+```mermaid
+graph LR
+    A[Client<br/>client.sh] -->|TCP:7777| B[Server<br/>server.sh]
+    B --> C[OS Detection<br/>detect_os.sh]
+    C --> D{Operating System}
+    D -->|Linux| E[nc -l -p 7777]
+    D -->|macOS| F[nc -l 7777]
+    D -->|Windows| G[ncat -l 7777]
+```
+
+## File structure
+
+```
+project/
+├── server.sh          # TCP server implementation
+├── client.sh          # TCP client implementation
+├── detect_os.sh       # Cross-platform OS detection
+└── README.md          # This documentation
+```
+
+## Prerequisites
+
+### Linux/macOS
+```bash
+# Usually pre-installed, but if needed:
+sudo apt install netcat-openbsd  # Ubuntu/Debian
+brew install netcat              # macOS with Homebrew
+```
+
+### Windows
+```bash
+# Option 1: Chocolatey
+choco install netcat
+
+# Option 2: Download ncat from nmap.org
+# https://nmap.org/download.html
+
+# Option 3: WSL (Windows Subsystem for Linux)
+wsl sudo apt install netcat-openbsd
+```
+
+## Usage
+
+### Make scripts executable
+```bash
+chmod +x server.sh client.sh detect_os.sh
+```
+
+### Start the server
+```bash
+./server.sh
+```
+Expected output:
+```
+OS detected: Linux
+Starting server on Linux...
+Listening on port 7777...
+```
+
+### Run the client (make sure to be in another terminal)
+```bash
+./client.sh
+```
+Example interaction:
+```
+Enter the server address [localhost]:
+Enter the message: Hello from client!
+Sending message to localhost...
+```
+
+### Server receives the message
+```
+Message received: Hello from client!
+Connection closed, restarting server...
+```
+
+## Features
+
+### Cross platform OS detection
+The `detect_os.sh` script automatically detects:
+- **Linux**: Uses `nc -l -p 7777`
+- **macOS**: Uses `nc -l 7777`
+- **Windows**: Tries `ncat` first, falls back to `nc` variants
+
+### Client features
+- **Default server**: Uses `localhost` as default (just press Enter)
+- **Custom server**: Specify IP address or hostname
+- **Input validation**: Handles empty inputs gracefully
+
+### Server features
+- **OS-specific**: Adapts netcat syntax based on detected OS
+- **Error handling**: Graceful handling of missing netcat installations
+
+## Code explanation
+
+### OS detection logic
+```bash
+detect_os() {
+    case "$(uname -s)" in
+        Linux*)   os_type="Linux" ;;
+        Darwin*)  os_type="macOS" ;;
+        CYGWIN*|MINGW32*|MSYS*|MINGW*) os_type="Windows" ;;
+        *)        os_type="Unknown" ;;
+    esac
+    export DETECTED_OS="$os_type"
+}
+```
+
+### Default value handling
+```bash
+# If user presses Enter, use localhost
+server_address=${server_address:-$default_server}
+```
+
+### Cross platform netcat
+```bash
+case "$DETECTED_OS" in
+    "Linux")   nc -l -p 7777 ;;
+    "macOS")   nc -l 7777 ;;
+    "Windows") ncat -l 7777 || nc -l 7777 ;;
+esac
+```
+
+## Testing
+
+### Test basic communication
+```bash
+# Terminal 1
+./server.sh
+
+# Terminal 2
+./client.sh
+# Enter: localhost
+# Message: "Test message"
+```
+
+### Test remote connection
+```bash
+# On server machine
+./server.sh
+
+# On client machine (replace with server IP)
+./client.sh
+# Enter: 192.168.1.100
+# Message: "Remote test"
+```
+## Troubleshooting
+
+### Server won't start
+```bash
+# Check if port is in use
+netstat -tulpn | grep 7777
+
+# Kill existing process
+sudo killall nc
+```
+
+### Client can't connect
+```bash
+# Test connectivity
+ping server_address
+telnet server_address 7777
+```
+
+### Netcat not found (Windows)
+```bash
+# Install options
+choco install netcat                    # Chocolatey
+winget install nmap                     # Windows Package Manager
+# Or download from https://nmap.org/
+```
+
+## Contributing
+
+Feel free to submit issues and enhancement requests!

Projects/0_bash_TCP_server/client.sh

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+#!/bin/bash
+
+default_server="localhost"
+
+read -p "Enter the server address [$default_server]: " server_address
+
+server_address=${server_address:-$default_server}
+
+read -p "Enter the message: " message
+
+echo "Sending message to $server_address..."
+echo "$message" | nc $server_address 7777

Projects/0_bash_TCP_server/detect_os.sh

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+#!/bin/bash
+
+detect_os() {
+    local os_type=""
+    local os_info=""
+
+    case "$(uname -s)" in
+        Linux*)
+            os_type="Linux"
+            if [ -f /etc/os-release ]; then
+                . /etc/os-release
+                os_info="$NAME $VERSION"
+            fi
+            ;;
+        Darwin*)
+            os_type="macOS"
+            os_info=$(sw_vers -productVersion)
+            ;;
+        CYGWIN*|MINGW32*|MSYS*|MINGW*)
+            os_type="Windows"
+            ;;
+        *)
+            os_type="Unknown"
+            os_info="$(uname -s)"
+            ;;
+    esac
+
+    export DETECTED_OS="$os_type"
+    export OS_INFO="$os_info"
+
+    echo "$os_type"
+}
+
+get_os_details() {
+    detect_os > /dev/null
+    echo "OS: $DETECTED_OS"
+    if [ -n "$OS_INFO" ]; then
+        echo "Info: $OS_INFO"
+    fi
+}

Projects/0_bash_TCP_server/server.sh

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+#!/bin/bash
+source detect_os.sh
+
+detect_os > /dev/null
+echo "OS détecté : $DETECTED_OS"
+
+
+if [ "$DETECTED_OS" = "Linux" ]; then
+    echo "Starting server on Linux..."
+    nc -l -p 7777
+elif [ "$DETECTED_OS" = "macOS" ]; then
+    echo "Starting server on macOS..."
+    nc -l 7777
+elif [ "$DETECTED_OS" = "Windows" ]; then
+    echo "Starting server on Windows..."
+    # Test multiple syntaxes
+    if command -v ncat >/dev/null 2>&1; then
+        ncat -l 7777
+    elif command -v nc >/dev/null 2>&1; then
+        # Test both possible syntaxes
+        nc -l 7777 2>/dev/null || nc -l -p 7777
+    else
+        echo "Netcat not found. Installation required."
+        echo "Install with: choco install netcat or download ncat"
+    fi
+else
+    echo "Unsupported OS: $DETECTED_OS"
+fi