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CS144 Writeup(concise)

Last Sync: 2025-09-26, Checkpoint 0

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用时2h左右，本次作业主要涉及环境配置、telnet和netcat模拟简单的Client/Server交互，以及对无限字节流ByteStream的理解和实现。

Setup

  • 基础开发环境配置
# Ubuntu
sudo apt update
sudo apt install git cmake gdb build-essential clang clang-tidy clang-format gcc-doc pkg-config glibc-doc tcpdump tshark

# Fedora
sudo dnf install git cmake gdb @development-tools clang clang-tools-extra pkgconf-pkg-config glibc-devel tcpdump wireshark-cli 
# Extra packages(maybe not needed)
sudo dnf install libubsan libasan
  • git
  • 配置：可参考cs144-2025-winter备份仓库，创建自己的私有仓库并添加cs144-grader为协作者

About Git: make frequent small commits as you work, and use commit messages that identify what changed and why.

  • CS144的cpp开发准则：
  • RAII(Resource Acquisition Is Initialization)：资源获取即初始化
    • 每个对象的public接口尽量少
    • 内部有安全检查，减少误用
    • 避免“成对操作”（如 malloc/free 或 new/delete），而是通过构造/析构等自动清理资源
  • 其他比较常见的准则：
    • 避免裸指针
    • 使用std::string而不是C风格字符串
    • 尽可能使用const
  • CS144对C的底层函数进行了Modern C++封装，需要阅读util/socket.hh, util/file_descriptor.hh等头文件了解其接口

Warmup

  • 使用telnet建立外部连接(Role: Client): Hello World和Email sending(需要SUNet ID，故跳过)
GET /hello HTTP/1.1
Host: cs144.keithw.org
Connection: close
  # Press Enter twice after the last line
  • 使用netcat建立本地连接(Role: Server): Hello World
netcat -v -l -p 9090  # Server
telnet localhost 9090 # Client

Writing a network program using an OS stream socket

  • Stream Socket
  • Unreliable Internet always give its "best effort" to deliver datagrams, which is self-contained and made up of some metadata(source/destination IP/port) and payload(data, up to about 1500 bytes).
  • Endpoint OS's role: turn "best effort" datagram into "reliable" bytestream.

(In-Memory) Reliable Byte Stream

首先为byte_stream.hh添加protected成员变量:

  • buffer_：实际存储数据的容器，需要先初始化为空字符串，否则报错：‘ByteStream::buffer_’应该在成员初始化列表中被初始化 [-Werror=effc++]
  • closed_：流是否已关闭
  • bytes_pushed_：累计写入字节数
  • bytes_popped_：累计弹出字节数

剩余部分，管理好这些成员变量状态即可。