Hey there! Let's break this down step by step since you've got solid programming fundamentals but are new to networking for app development. Your goal is totally achievable without becoming a network admin—we'll focus only on what you need to build your custom tool.

First: Learn the Minimal Networking Basics You Need #

You don't need to dive into textbooks on network architecture. Just spend 1-2 days wrapping your head around these core concepts:

• TCP/UDP Fundamentals: Understand that TCP is for connection-based traffic (like browsing, messaging) and UDP is for fast, unconnected traffic (like video calls). Know the basics of a TCP connection "handshake"—this is what triggers your "new connection" alert.
• Process-Network Link: Grasp how operating systems tie network activity to specific processes (each network connection is linked to a Process ID, or PID).
• Network Interfaces: Know that your device uses interfaces (WiFi, mobile data, Ethernet) to send/receive data—you'll need to target these to track traffic.

Choose Your Tools: Libraries & Frameworks by Platform #

Since you need support for both Windows and Android, let's split this by OS:

Windows Platform (Great for Your C++ Background) #

You can pick up C++ again, or use C# for faster development—both work well here:

• Npcap: The updated, Windows-friendly version of WinPCap. It lets you capture all network packets passing through your system's interfaces, and can link packets to specific PIDs. Perfect for tracking per-process data usage.
• Windows Filtering Platform (WFP): A native Windows API that lets you control network traffic—blocking a process's internet access, setting data quotas, or triggering alerts when new connections are made. It's far more stable than third-party firewalls for system-level control.
• C# Alternatives (If You Want to Skip C++): Use SharpPcap (a C# wrapper for Npcap) and WindowsFirewallHelper (simplifies WFP rule creation) to build the same features with less low-level code.

Android Platform #

Stick to native Kotlin or Java for the most control over system APIs:

• NetworkStatsManager: A built-in Android API that lets you fetch per-app data usage (split by mobile data/WiFi) without needing root access. Ideal for tracking which apps are eating your data.
• VpnService: The official Android API for creating a lightweight virtual VPN. All app network traffic passes through this service, so you can intercept connections, block access, and trigger alerts. No root required—this is the standard way to build network control tools on Android.
• Kotlin Coroutines: Essential for running background tasks (like traffic monitoring) without freezing your app's UI.

Step-by-Step Development Plan #

Start small and iterate—don't try to build everything at once:

1. Windows First (Easier to Relearn with Your C++ Background) #

• Phase 1: Track Process Traffic:
  Write a simple command-line program using Npcap to capture packets. Use Windows APIs like GetExtendedTcpTable to link each packet's connection to a PID, then calculate total bytes sent/received per process. Output this data in real time.
• Phase 2: Add Connection Alerts:
  Monitor for new TCP connections (either by capturing SYN packets with Npcap or using WFP's connection-tracking events). When a new connection is detected, pop up a notification showing the process name and target IP/website.
• Phase 3: Add Control Features:
  Use WFP to create rules that let you block a process's network access with a click, or set a data quota—automatically block the process if it exceeds your limit.

2. Move to Android #

• Phase 1: Monitor App Traffic:
  Build a basic UI using NetworkStatsManager to display each app's daily/monthly data usage. Add filters to separate mobile data from WiFi.
• Phase 2: Alerts & Control:
  Implement VpnService to intercept all network requests. When an app initiates a new connection, trigger a system notification. Add a toggle in your app to block specific apps from accessing the internet, or set data limits that trigger automatic blocking.

Key Tips to Avoid Overcomplicating #

• Don't Reinvent the Wheel: Use pre-built libraries for low-level tasks (like Npcap for packet capture) so you can focus on your core features (tracking, alerts, control).
• Test with Known Apps: Validate your tool using apps you use daily (Chrome, WhatsApp, etc.) to make sure traffic stats are accurate and alerts trigger correctly.
• Handle Permissions Upfront: Windows requires admin rights to capture packets and modify firewall rules; Android needs ACCESS_NETWORK_STATE, PACKAGE_USAGE_STATS, and VPN permissions. Make sure your app clearly explains why it needs these.

You've got the programming foundation to pull this off—focus on one platform at a time, and don't stress about becoming a networking expert. You only need to learn the parts that directly serve your tool's goals.

内容的提问来源于stack exchange，提问作者Agaba Akuh