diff --git a/.clang-format b/.clang-format
new file mode 100644
index 0000000..05e8913
--- /dev/null
+++ b/.clang-format
@@ -0,0 +1,75 @@
+# Clang-Format configuration file
+# Based on Google C++ style with moderate adjustments
+
+Language: Cpp
+BasedOnStyle: Google
+
+# Indentation
+IndentWidth: 4
+TabWidth: 4
+UseTab: Never
+AccessModifierOffset: -4
+
+# Line width
+ColumnLimit: 100
+
+# Braces
+BreakBeforeBraces: Attach
+AllowShortIfStatementsOnASingleLine: Never
+AllowShortLoopsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: Empty
+AllowShortBlocksOnASingleLine: Empty
+
+# Pointer and reference alignment
+PointerAlignment: Left
+ReferenceAlignment: Left
+
+# Include file sorting
+SortIncludes: CaseSensitive
+IncludeBlocks: Regroup
+IncludeCategories:
+  # 1. Project headers
+  - Regex: '^"(client|server|common|protocol)/'
+    Priority: 1
+  # 2. Third-party libraries
+  - Regex: '^<.*\.h>'
+    Priority: 2
+  # 3. C++ standard library
+  - Regex: '^<.*>'
+    Priority: 3
+
+# Namespace
+NamespaceIndentation: None
+CompactNamespaces: false
+FixNamespaceComments: true
+
+# Alignment
+AlignAfterOpenBracket: Align
+AlignConsecutiveAssignments: false
+AlignConsecutiveDeclarations: false
+AlignOperands: true
+AlignTrailingComments: true
+
+# Line breaking
+AllowAllParametersOfDeclarationOnNextLine: true
+BinPackArguments: true
+BinPackParameters: true
+BreakConstructorInitializers: BeforeColon
+ConstructorInitializerAllOnOneLineOrOnePerLine: true
+
+# Spacing
+SpaceAfterCStyleCast: false
+SpaceAfterTemplateKeyword: true
+SpaceBeforeAssignmentOperators: true
+SpaceBeforeParens: ControlStatements
+SpacesInAngles: false
+SpacesInParentheses: false
+SpacesInSquareBrackets: false
+
+# C++11 features
+Standard: c++17
+Cpp11BracedListStyle: true
+
+# Comments
+ReflowComments: true
+SpacesBeforeTrailingComments: 2
diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..baeab80
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,52 @@
+# EditorConfig helps maintain consistent coding styles across different editors
+# https://editorconfig.org
+
+root = true
+
+# Default settings (applies to all files)
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 4
+
+# C/C++ files
+[*.{c,cc,cpp,h,hpp}]
+indent_size = 4
+
+# CMake files
+[CMakeLists.txt]
+indent_size = 4
+
+[*.cmake]
+indent_size = 4
+
+# Markdown files (preserve trailing spaces for line breaks)
+[*.md]
+trim_trailing_whitespace = false
+
+# YAML files
+[*.{yml,yaml}]
+indent_size = 2
+
+# JSON files
+[*.json]
+indent_size = 2
+
+# Shell scripts
+[*.sh]
+indent_size = 2
+
+# Batch scripts
+[*.bat]
+end_of_line = crlf
+
+# Makefile (must use tabs)
+[Makefile]
+indent_style = tab
+
+# Docker files
+[Dockerfile*]
+indent_size = 4
diff --git a/.github/ISSUE_TEMPLATE/bug_report.md b/.github/ISSUE_TEMPLATE/bug_report.md
new file mode 100644
index 0000000..9412c8d
--- /dev/null
+++ b/.github/ISSUE_TEMPLATE/bug_report.md
@@ -0,0 +1,37 @@
+---
+name: Bug 报告
+about: 报告一个 bug 帮助我们改进
+title: '[BUG] '
+labels: bug
+assignees: ''
+---
+
+## 🐛 Bug 描述
+简要描述这个 bug 是什么。
+
+## 📝 复现步骤
+1. 执行 '...'
+2. 运行命令 '...'
+3. 查看错误
+
+## ✅ 期望行为
+描述你期望发生什么。
+
+## ❌ 实际行为
+描述实际发生了什么。
+
+## 🖥️ 环境信息
+- 操作系统: [例如 Ubuntu 22.04 / Windows 11]
+- 编译器: [例如 GCC 11.4 / MSVC 19.36]
+- CMake 版本: [例如 3.22]
+
+## 📋 日志输出
+```
+粘贴相关日志输出
+```
+
+## 📷 截图
+如有必要，添加截图。
+
+## 💡 其他信息
+添加任何其他有关该问题的上下文。
diff --git a/.github/ISSUE_TEMPLATE/feature_request.md b/.github/ISSUE_TEMPLATE/feature_request.md
new file mode 100644
index 0000000..b46c34c
--- /dev/null
+++ b/.github/ISSUE_TEMPLATE/feature_request.md
@@ -0,0 +1,29 @@
+---
+name: 功能请求
+about: 提出新功能或改进建议
+title: '[FEATURE] '
+labels: enhancement
+assignees: ''
+---
+
+## 🚀 功能描述
+简要描述你想要的功能。
+
+## 💡 动机
+为什么需要这个功能？它解决什么问题？
+
+## 📋 详细设计（可选）
+如果你有实现思路，请描述：
+
+### 方案
+描述你提议的解决方案。
+
+### 替代方案
+你考虑过的其他方案。
+
+## ✅ 验收标准
+- [ ] 标准 1
+- [ ] 标准 2
+
+## 📚 参考资料
+相关链接、文档或示例。
diff --git a/.github/PULL_REQUEST_TEMPLATE.md b/.github/PULL_REQUEST_TEMPLATE.md
new file mode 100644
index 0000000..c0b089c
--- /dev/null
+++ b/.github/PULL_REQUEST_TEMPLATE.md
@@ -0,0 +1,33 @@
+## 📋 PR Description
+Briefly describe what this PR does.
+
+## 🔗 Related Issue
+Closes #(issue number)
+
+## 🔄 Change Type
+Please check the applicable options:
+
+- [ ] 🐛 Bug fix (fix)
+- [ ] ✨ New feature (feat)
+- [ ] 📝 Documentation update (docs)
+- [ ] 🎨 Code format/style (style)
+- [ ] ♻️ Code refactoring (refactor)
+- [ ] ✅ Test related (test)
+- [ ] 🔧 Build/configuration (chore)
+
+## 📝 Change Details
+- Change 1
+- Change 2
+
+## ✅ Self-Check List
+- [ ] Code compiles successfully
+- [ ] All tests pass
+- [ ] Necessary tests added
+- [ ] Related documentation updated
+- [ ] Commit messages follow conventions
+
+## 🧪 Testing Instructions
+Describe how to test these changes.
+
+## 📷 Screenshots (if applicable)
+Screenshots of UI changes.
diff --git a/.gitignore b/.gitignore
index 670a86b..2186dc2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,8 +1,8 @@
-# IDE 个人化配置
+# IDE personal configurations
 .vscode/
 *.code-workspace
 
-# OS 文件
+# OS files
 .DS_Store
 Thumbs.db
 desktop.ini
@@ -10,15 +10,15 @@ desktop.ini
 *.swo
 *~
 
-# 构建产物（如果根目录构建）
+# Build artifacts (if built in root directory)
 build/
 out/
 bin/
 dist/
 
-# 日志
+# Logs
 *.log
 
-# 临时文件
+# Temporary files
 *.tmp
 *.temp
diff --git a/CODE_OF_CONDUCT.md b/CODE_OF_CONDUCT.md
new file mode 100644
index 0000000..2aaa013
--- /dev/null
+++ b/CODE_OF_CONDUCT.md
@@ -0,0 +1,75 @@
+# Contributor Covenant Code of Conduct
+
+[![中文](https://img.shields.io/badge/lang-中文-red.svg)](CODE_OF_CONDUCT.zh-CN.md)
+
+## Our Pledge
+
+We as members, contributors, and leaders pledge to make participation in our
+community a harassment-free experience for everyone, regardless of age, body
+size, visible or invisible disability, ethnicity, sex characteristics, gender
+identity and expression, level of experience, education, socio-economic status,
+nationality, personal appearance, race, religion, or sexual identity
+and orientation.
+
+We pledge to act and interact in ways that contribute to an open, welcoming,
+diverse, inclusive, and healthy community.
+
+## Our Standards
+
+Examples of behavior that contributes to a positive environment for our
+community include:
+
+* Demonstrating empathy and kindness toward other people
+* Being respectful of differing opinions, viewpoints, and experiences
+* Giving and gracefully accepting constructive feedback
+* Accepting responsibility and apologizing to those affected by our mistakes,
+  and learning from the experience
+* Focusing on what is best not just for us as individuals, but for the
+  overall community
+
+Examples of unacceptable behavior include:
+
+* The use of sexualized language or imagery, and sexual attention or
+  advances of any kind
+* Trolling, insulting or derogatory comments, and personal or political attacks
+* Public or private harassment
+* Publishing others' private information, such as a physical or email
+  address, without their explicit permission
+* Other conduct which could reasonably be considered inappropriate in a
+  professional setting
+
+## Enforcement Responsibilities
+
+Community leaders are responsible for clarifying and enforcing our standards of
+acceptable behavior and will take appropriate and fair corrective action in
+response to any behavior that they deem inappropriate, threatening, offensive,
+or harmful.
+
+Community leaders have the right and responsibility to remove, edit, or reject
+comments, commits, code, wiki edits, issues, and other contributions that are
+not aligned to this Code of Conduct, and will communicate reasons for moderation
+decisions when appropriate.
+
+## Scope
+
+This Code of Conduct applies within all community spaces, and also applies when
+an individual is officially representing the community in public spaces.
+Examples of representing our community include using an official e-mail address,
+posting via an official social media account, or acting as an appointed
+representative at an online or offline event.
+
+## Enforcement
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported by creating an issue in this repository. All complaints will be reviewed and investigated promptly and fairly.
+
+All community leaders are obligated to respect the privacy and security of the
+reporter of any incident.
+
+## Attribution
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage],
+version 2.0, available at
+https://www.contributor-covenant.org/version/2/0/code_of_conduct.html.
+
+[homepage]: https://www.contributor-covenant.org
diff --git a/CODE_OF_CONDUCT.zh-CN.md b/CODE_OF_CONDUCT.zh-CN.md
new file mode 100644
index 0000000..0b6860b
--- /dev/null
+++ b/CODE_OF_CONDUCT.zh-CN.md
@@ -0,0 +1,46 @@
+# 贡献者行为准则
+
+[![English](https://img.shields.io/badge/lang-English-blue.svg)](CODE_OF_CONDUCT.md)
+
+## 我们的承诺
+
+为了营造一个开放和友好的环境，我们作为贡献者和维护者承诺：无论年龄、体型、残疾、种族、性别特征、性别认同和表达、经验水平、教育程度、社会经济地位、国籍、外貌、种族、宗教或性取向如何，参与我们项目和社区的每个人都不会受到骚扰。
+
+## 我们的标准
+
+有助于创造积极环境的行为包括：
+
+* 使用友好和包容的语言
+* 尊重不同的观点和经验
+* 优雅地接受建设性批评
+* 专注于对社区最有利的事情
+* 对其他社区成员表示同理心
+
+不可接受的参与者行为包括：
+
+* 使用性暗示的语言或图像，以及不受欢迎的性关注或性挑逗
+* 恶意挑衅、侮辱/贬损性评论以及个人或政治攻击
+* 公开或私下骚扰
+* 未经明确许可，发布他人的私人信息，如住址或电子邮件地址
+* 其他可以合理地被认为在专业环境中不适当的行为
+
+## 我们的责任
+
+项目维护者有责任为可接受的行为标准做出诠释，并对任何不可接受的行为采取恰当且公平的纠正措施。
+
+项目维护者有权且有责任删除、编辑或拒绝与本行为准则不符的评论、提交、代码、wiki 编辑、Issue 和其他贡献，并可以暂时或永久性地封禁任何他们认为行为不适当、威胁、冒犯或有害的贡献者。
+
+## 适用范围
+
+本行为准则适用于所有项目空间，当个人在公共空间代表项目或其社区时也适用。代表项目或社区的例子包括使用官方项目电子邮件地址、通过官方社交媒体账户发布消息，或在线上或线下活动中担任指定代表。
+
+## 执行
+
+如遇到辱骂、骚扰或其他不可接受的行为，可以通过创建 Issue 联系项目团队进行举报。所有投诉都将被审查和调查，并将做出被认为必要且适合具体情况的回应。项目团队有义务对事件举报者保密。
+
+## 归属
+
+本行为准则改编自 [Contributor Covenant][homepage] 2.0 版，
+可在 https://www.contributor-covenant.org/version/2/0/code_of_conduct.html 获取。
+
+[homepage]: https://www.contributor-covenant.org
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..b3055a2
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,124 @@
+# Contributing Guide
+
+[![中文](https://img.shields.io/badge/lang-中文-red.svg)](CONTRIBUTING.zh-CN.md)
+
+Thank you for your interest in contributing to this project! Here's how you can help.
+
+## 🌿 Branching Strategy
+
+We use a simplified Git Flow model:
+
+| Branch | Purpose | Protection |
+|--------|---------|------------|
+| `main` | Stable releases | Protected, PR required |
+| `develop` | Development integration | PR required |
+| `feature/*` | New features | Personal branches |
+| `bugfix/*` | Bug fixes | Personal branches |
+
+### Branch Naming Convention
+
+```
+feature/add-compression
+feature/file-encryption
+bugfix/fix-connection-timeout
+bugfix/memory-leak-fix
+docs/update-readme
+```
+
+## 📝 How to Contribute
+
+### 1. Fork & Clone
+
+```bash
+# After forking the repository
+git clone https://github.com/YOUR_USERNAME/Computer_Network_lab.git
+cd Computer_Network_lab
+git remote add upstream https://github.com/FrankieLiu04/Computer_Network_lab.git
+```
+
+### 2. Create a Feature Branch
+
+```bash
+git checkout develop
+git pull upstream develop
+git checkout -b feature/your-feature-name
+```
+
+### 3. Develop & Commit
+
+```bash
+# Make your changes...
+git add .
+git commit -m "feat: add your feature description"
+```
+
+#### Commit Message Convention
+
+We follow [Conventional Commits](https://www.conventionalcommits.org/) specification:
+
+| Type | Description |
+|------|-------------|
+| `feat` | New feature |
+| `fix` | Bug fix |
+| `docs` | Documentation update |
+| `style` | Code style (no logic change) |
+| `refactor` | Code refactoring |
+| `test` | Test related |
+| `chore` | Build/tooling changes |
+
+Examples:
+```
+feat: add resumable file upload
+fix: resolve memory overflow for large files
+docs: update Docker deployment guide
+```
+
+### 4. Push & Create PR
+
+```bash
+git push origin feature/your-feature-name
+```
+
+Then create a Pull Request on GitHub targeting the `develop` branch.
+
+## ✅ PR Checklist
+
+Before submitting your PR, please verify:
+
+- [ ] Code compiles successfully
+- [ ] All tests pass (`ctest` or CI)
+- [ ] Code follows style guidelines
+- [ ] Documentation updated (if needed)
+- [ ] Commit messages follow conventions
+
+## 🏗️ Development Environment
+
+### Requirements
+
+- CMake 3.16+
+- C++17 compatible compiler
+- Docker (optional, for containerized testing)
+
+### Build
+
+```bash
+cd reliable-remote-backup-system
+cmake -B build -DCMAKE_BUILD_TYPE=Debug
+cmake --build build
+```
+
+### Test
+
+```bash
+cd build
+ctest --output-on-failure
+```
+
+## 💬 Getting Help
+
+- Questions? Create an [Issue](https://github.com/FrankieLiu04/Computer_Network_lab/issues)
+- Want to discuss? Use the `question` label
+
+## 📜 Code of Conduct
+
+Please read our [Code of Conduct](CODE_OF_CONDUCT.md) to maintain a friendly and inclusive environment.
diff --git a/CONTRIBUTING.zh-CN.md b/CONTRIBUTING.zh-CN.md
new file mode 100644
index 0000000..7ea10af
--- /dev/null
+++ b/CONTRIBUTING.zh-CN.md
@@ -0,0 +1,124 @@
+# 贡献指南
+
+[![English](https://img.shields.io/badge/lang-English-blue.svg)](CONTRIBUTING.md)
+
+感谢你对本项目的兴趣！以下是参与贡献的指南。
+
+## 🌿 分支策略
+
+我们采用简化的 Git Flow 模型：
+
+| 分支 | 用途 | 保护级别 |
+|------|------|----------|
+| `main` | 稳定发布版本 | 受保护,需要 PR |
+| `develop` | 开发集成分支 | 需要 PR |
+| `feature/*` | 新功能开发 | 个人分支 |
+| `bugfix/*` | Bug 修复 | 个人分支 |
+
+### 分支命名规范
+
+```
+feature/add-compression
+feature/file-encryption
+bugfix/fix-connection-timeout
+bugfix/memory-leak-fix
+docs/update-readme
+```
+
+## 📝 如何贡献
+
+### 1. Fork & Clone
+
+```bash
+# Fork 本仓库后
+git clone https://github.com/你的用户名/Computer_Network_lab.git
+cd Computer_Network_lab
+git remote add upstream https://github.com/FrankieLiu04/Computer_Network_lab.git
+```
+
+### 2. 创建功能分支
+
+```bash
+git checkout develop
+git pull upstream develop
+git checkout -b feature/你的功能名称
+```
+
+### 3. 开发 & 提交
+
+```bash
+# 进行开发...
+git add .
+git commit -m "feat: 添加新功能描述"
+```
+
+#### Commit 消息规范
+
+我们使用 [Conventional Commits](https://www.conventionalcommits.org/) 规范：
+
+| 类型 | 说明 |
+|------|------|
+| `feat` | 新功能 |
+| `fix` | Bug 修复 |
+| `docs` | 文档更新 |
+| `style` | 代码格式（不影响逻辑） |
+| `refactor` | 重构 |
+| `test` | 测试相关 |
+| `chore` | 构建/工具变动 |
+
+示例：
+```
+feat: 添加文件断点续传功能
+fix: 修复大文件传输时的内存溢出问题
+docs: 更新 Docker 部署文档
+```
+
+### 4. 推送 & 创建 PR
+
+```bash
+git push origin feature/你的功能名称
+```
+
+然后在 GitHub 上创建 Pull Request，目标分支选择 `develop`。
+
+## ✅ PR 检查清单
+
+提交 PR 前请确认：
+
+- [ ] 代码能够正常编译
+- [ ] 所有测试通过 (`ctest` 或 CI)
+- [ ] 遵循代码风格规范
+- [ ] 更新了相关文档（如需要）
+- [ ] Commit 消息符合规范
+
+## 🏗️ 本地开发环境
+
+### 依赖
+
+- CMake 3.16+
+- C++17 兼容编译器
+- Docker（可选，用于容器化测试）
+
+### 构建
+
+```bash
+cd reliable-remote-backup-system
+cmake -B build -DCMAKE_BUILD_TYPE=Debug
+cmake --build build
+```
+
+### 测试
+
+```bash
+cd build
+ctest --output-on-failure
+```
+
+## 💬 寻求帮助
+
+- 有问题？创建 [Issue](https://github.com/FrankieLiu04/Computer_Network_lab/issues)
+- 想讨论？使用 Issue 的 `question` 标签
+
+## 📜 行为准则
+
+请阅读我们的 [行为准则](CODE_OF_CONDUCT.zh-CN.md)，确保友好、包容的协作环境。
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..c6f892c
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 FrankieLiu04
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/README.md b/README.md
index dedef4a..92b573d 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,6 @@
 # Computer Network Lab — Reliable Remote Backup System
 
+[![中文](https://img.shields.io/badge/lang-中文-red.svg)](README.zh-CN.md)
 [![CI](https://github.com/FrankieLiu04/Computer_Network_lab/actions/workflows/ci.yml/badge.svg)](https://github.com/FrankieLiu04/Computer_Network_lab/actions/workflows/ci.yml)
 [![C++17](https://img.shields.io/badge/C%2B%2B-17-blue.svg)](https://isocpp.org/)
 [![Docker](https://img.shields.io/badge/Docker-Ready-2496ED?logo=docker&logoColor=white)](https://www.docker.com/)
diff --git a/original-labs/stable.c b/original-labs/stable.c
index 80b11eb..90a12a1 100644
--- a/original-labs/stable.c
+++ b/original-labs/stable.c
@@ -114,7 +114,7 @@ void ComputeChecksum(struct pkt *packet)
     unsigned int sum = 0;
     sum += packet->seqnum;
     sum += packet->acknum;
-    
+
     for(int i=0; i<20; i++) {
         sum += (unsigned char)packet->payload[i];
         if(sum & 0xFFFF0000) {
@@ -129,7 +129,7 @@ int CheckCorrupted(struct pkt packet)
     unsigned int sum = 0;
     sum += packet.seqnum;
     sum += packet.acknum;
-    
+
     for(int i=0; i<20; i++) {
         sum += (unsigned char)packet.payload[i];
         if(sum & 0xFFFF0000) {
@@ -145,10 +145,10 @@ int CheckCorrupted(struct pkt packet)
 void A_output(struct msg_ message)
 {
     struct timer *pkt_timer;
-    
+
     /* Create pkt before window is full */
     if (nextseqnum < base + WINDOWSIZE) {
-        /* 创建新数据包 */
+        /* Create new data packet */
         struct pkt packet;
         packet.seqnum = nextseqnum;
         packet.acknum = NOTUSED;
@@ -223,7 +223,7 @@ void A_input(struct pkt packet)
         return; // if no matching ACK found, just return
     }
 
-    
+
     while (pktnum > 0 && winbuf[winfront].acknum == 1 && winbuf[winfront].seqnum == base) {
         base++;
         winfront = (winfront + 1) % WINDOWSIZE;
@@ -231,7 +231,7 @@ void A_input(struct pkt packet)
         ack_adv_num++;
     }
 
-  
+
     while (msg_num > 0 && nextseqnum < base + WINDOWSIZE) {
         struct msg_ message = buffer[buffront];
         buffront = (buffront + 1) % MAXBUFSIZE;
@@ -243,11 +243,11 @@ void A_input(struct pkt packet)
         memcpy(new_pkt.payload, message.data, 20);
         ComputeChecksum(&new_pkt);
 
-        
+
         printf("[%.1f] A: send packet [%d] base [%d]\n", currenttime_(), nextseqnum, base);
         tolayer3(A, new_pkt);
         packet_sent++; // update packet sent counter
-        
+
         winbuf[winrear] = new_pkt;
         winbuf[winrear].acknum = 0; /* initializing */
         winrear = (winrear + 1) % WINDOWSIZE;
@@ -266,15 +266,15 @@ void A_input(struct pkt packet)
 void A_packet_time_rinterrupt(struct timer* pkt_timer)
 {
     packet_time_out++;
-    
+
     /* find pkt from buffer */
     int found = 0;
     for(int i=0; i<pktnum; i++) {
         if(winbuf[(winfront+i)%WINDOWSIZE].seqnum == pkt_timer->pkt_seq && winbuf[(winfront+i)%WINDOWSIZE].acknum == 0) {
-            
+
             printf("[%.1f] A: packet [%d] time_ out, resend packet\n", currenttime_(), pkt_timer->pkt_seq);
-            
-        
+
+
             tolayer3(A, winbuf[(winfront+i)%WINDOWSIZE]);
             packet_sent++; // add this line
             packet_resent++;
@@ -282,7 +282,7 @@ void A_packet_time_rinterrupt(struct timer* pkt_timer)
             break;
         }
     }
-    
+
     if(found) {
         starttime_r(pkt_timer, A, RTT);
     }
@@ -294,7 +294,7 @@ void B_input(struct pkt packet)
     static int expected_seq = 0;
     static struct pkt recv_window[8];
     static int recv_marked[8] = {0}; /* 0: not marked, 1: marked */
-    
+
     if (CheckCorrupted(packet)) {
         if (packet.seqnum == 999999) {
             printf("[%.1f] B: packet [999999] corrupted\n", currenttime_());
@@ -304,35 +304,35 @@ void B_input(struct pkt packet)
         /* remoce packet_corrupt++，since checked in tolayer3 */
         return;
     }
-    
+
     /* 2. check */
     if ((packet.seqnum >= expected_seq && packet.seqnum < expected_seq + WINDOWSIZE) ||
         (packet.seqnum < expected_seq && packet.seqnum >= expected_seq - WINDOWSIZE)) {
         int slot = packet.seqnum % WINDOWSIZE;
-        
+
         /* 3. buffer and sendACK */
         if (recv_marked[slot] == 0 || recv_window[slot].seqnum != packet.seqnum) {
             /* buffer */
             memcpy(&recv_window[slot], &packet, sizeof(struct pkt));
             recv_marked[slot] = 1;
-            
+
             /* send ack */
             struct pkt ack_pkt;
             ack_pkt.acknum = packet.seqnum;
             ack_pkt.seqnum = NOTUSED;
-            memset(ack_pkt.payload, 0, 20); /* 清空ACK包的payload */
+            memset(ack_pkt.payload, 0, 20); /* Clear ACK packet payload */
             ComputeChecksum(&ack_pkt);
             tolayer3(B, ack_pkt);
-            
+
             printf("[%.1f] B: packet [%d] received, send ACK [%d]\n", currenttime_(), packet.seqnum, packet.seqnum);
 
         }
-        
-   
-        while (recv_marked[expected_seq % WINDOWSIZE] == 1 && 
+
+
+        while (recv_marked[expected_seq % WINDOWSIZE] == 1 &&
                recv_window[expected_seq % WINDOWSIZE].seqnum == expected_seq) {
             tolayer5(B, recv_window[expected_seq % WINDOWSIZE].payload);
-            recv_marked[expected_seq % WINDOWSIZE] = 0; 
+            recv_marked[expected_seq % WINDOWSIZE] = 0;
             packet_receieve++;
             expected_seq++;
         }
@@ -344,7 +344,7 @@ void B_input(struct pkt packet)
         memset(ack_pkt.payload, 0, 20);
         ComputeChecksum(&ack_pkt);
         tolayer3(B, ack_pkt);
-        
+
 
         printf("[%.1f] B: packet [%d] received, send ACK [%d]\n", currenttime_(), packet.seqnum, packet.seqnum);
     }
@@ -381,13 +381,13 @@ void print_info() {
     printf("***********************************************************************************************************\n");
     printf("                                       Packet Transmission Summary                                         \n");
     printf("***********************************************************************************************************\n");
-    
-    /* 统计计算 - 每个包32KB，转换为Kb/s */
+
+    /* Statistics calculation - each packet is 32KB, convert to Kb/s */
     float throughput = (packet_receieve * 32.0 * 8) / currenttime_();
-    
+
     /* 正确传输的包数量应该等于总消息数量，即接收方接收到的包数量 */
     packet_correct = packet_receieve;
-    
+
     printf("From Sender to Receiver:  \n");
     printf(" total sent pkts:         %d \n", packet_sent);
     printf(" total correct pkts:      %d \n", packet_correct);
@@ -549,19 +549,19 @@ void init()                         /* initialize the simulator */
 //    float jimsrand();
 
     printf("Enter the number of messages to simulate: \n");
- 
+
     scanf("%d", &nsimmax);
     total_sim_msg = nsimmax * 32;
     printf("Enter time_ between messages from sender's layer5 [ > 0.0]:\n");
 
     scanf("%f", &lambda);
     printf("Enter channel pattern string\n");
-  
+
     scanf("%s", pattern);
     npttns = strlen(pattern);
 
     printf("Enter sender's window size\n");
-    
+
     scanf("%d", &WINDOWSIZE);
     winbuf = (struct pkt *) malloc(sizeof(struct pkt) * WINDOWSIZE);