ネットワーク・プログラミング（C言語）
Network Programming in C

第3回 10月16日 Lecture 3, October 16:
IP Networking Basics

Outline of This Lecture

• Review of last week's homework
• Tools and the Software Development Process
• The TCP/IP Protocol Stack in the Internet
• Internet Protocol addressing (v4/v6)
• Request/response operation
• Datagram v. stream
• Homework

Review of last week's homework

• Above, we defined the function MakeElementList(). Write a program including the function FreeElementList(), using the library function free().

#include <errno.h>

struct element {
  struct element *next;
  int elementNumber;
}

struct element *MakeElementList(int n) {
  struct element *tmp = malloc(sizeof(struct element));

  if (!tmp) {
    perror("MakeElementList"); exit(-1);
  }
  if (!n) {
    tmp->next = NULL;
  else {
    tmp->next = MakeElementList(n-1);
  }
  tmp->elementNumber = n;
  return tmp;
}

void PrintElementList(struct element *in) {
  printf("elementNumber: %d\n",in->elementNumber);
  if (in->next)
    PrintElementList(in->next);
}

void FreeElementList(struct element *in) {
  if (in->next)
    FreeElementList(in->next);
  free(in);
}

main()
{
  struct element *mylist;

  tmp = MakeElementList(10);
  if (!tmp)
    exit(-1);
  PrintElementList(tmp);
  FreeElementList(tmp);
}

Tools and the Software Development Process

• Defining the problem
  • This is critical!
• Designing your program
  • Good design saves implementation and debugging time.
  • Design (and code) defensively.
• Creating your program
  • Editors
  • Source code control
• Building your program
  • compiler
  • assembler
  • linker
  • make
• Understanding, fixing and improving your program
  • unit tests
  • debuggers
  • profilers

The TCP/IP Protocol Stack in the Internet

From Wikipedia:

Internet Protocol addressing (v4/v6)

• Address (IPv4 or IPv6)
• Upper-Layer Protocol identifier (e.g., TCP or UDP)
• Port number (if ULP is TCP or UDP)

And the IPv6 packet header:

After the IP header (whether v4 or v6), comes the transport-layer header. The only part of the transport-layer header we are interested in at the moment is the port number.

Request/Response (Client/Server) Operation

Datagram versus stream

宿題
Homework

1. Last week, you were supposed to create three source files and link them together for your program. This week, we are going to add unit test. We need two more source code files:
   • mylibtest.c
   • networkingtest.c
   Each of those should include a main() function that calls each function in the corresponding source file to test that it works. Now you must compile three separate programs: hotpotato, mylibtest, and networkingtest. Show that each one runs.
2. The homework "answer" at the top of this page does not actually work. Please copy that to your computer, and debug it. (You may also want to use this as an opportunity to try a source code control system, such as RCS, and my preference is that you send me the solution to this problem as a diff or rcsdiff from the existing program.)

Next Lecture

Additional Information

• Class top page
• Landweber/Murai networking class (with video and slides, 1999)

その他

• Rodney Van Meterのホームページ
• 徳田・村井・楠本・中村・高汐・重近・湧川・バンミーター研究プロジェクト