Beej的互联网套接字网络编程指南

需积分: 9 138 浏览量更新于2024-08-02 收藏 314KB PDF 举报

身份认证购VIP最低享 7 折!

30元优惠券

"Beej’s Guide to Network Programming Using Internet Sockets" 是一本由 Brian "Beej" Hall 编写的教程，专注于介绍如何在Linux环境中进行网络编程，特别是使用互联网套接字（Sockets）进行通信。这本书适用于对网络编程感兴趣的开发者，无论是初学者还是有经验的程序员。该指南涵盖了以下主要知识点： 1. **引言**: - **目标读者**（Audience）：适用于对网络编程感兴趣的任何人，尤其是那些想要在Linux平台上开发网络应用的开发者。 - **平台与编译器**（Platform and Compiler）：主要针对Linux环境，但也包含了一些关于Solaris/SunOS和Windows编程的注解。 - **官方主页**（Official Homepage）：提供了最新的版本信息和更新内容。 - **电子邮件政策**（Email Policy）：作者鼓励读者提问，但可能无法对所有邮件做出回应。 - **镜像**（Mirroring）：允许在其他网站上镜像该指南，以便更广泛地传播。 - **翻译注意事项**（Not for Translators）：对于那些想翻译该指南的人提供了指导。 - **版权和分布**（Copyright and Distribution）：遵循特定的开源许可，允许自由分发和使用。 2. **什么是套接字？**（What is a socket?）： - **两种类型的互联网套接字**（Two Types of Internet Sockets）：分为流式套接字（TCP）和数据报套接字（UDP），分别对应面向连接和无连接的通信模式。 - **网络理论**（Low-level Nonsense and Network Theory）：简述了网络通信的基本原理。 3. **结构体和数据处理**（structs and Data Handling）： - **转换本地类型**（Convert the Natives!）：在不同操作系统间，处理网络字节序和主机字节序的转换。 - **IP地址处理**（IP Addresses and How to Deal With Them）：介绍了如何处理和操作IP地址。 4. **系统调用**（System Calls or Bust）： - **socket()**：创建一个新的套接字文件描述符。 - **bind()**：将套接字与特定的IP地址和端口号绑定。 - **connect()**：建立到远程服务器的连接。 - **listen()**：使服务器进入监听状态，等待客户端的连接请求。 - **accept()**：接收并处理新的客户端连接请求。 - **send() 和 recv()**：用于发送和接收数据，适用于流式套接字。 - **sendto() 和 recvfrom()**：与send()和recv()类似，但适用于数据报套接字，可以指定发送或接收的数据源。 - **close() 和 shutdown()**：关闭套接字或停止发送/接收数据。 - **getpeername()**：获取连接的对端（远程）主机信息。 - **gethostbyname()**：根据域名查找对应的IP地址。该指南详细解释了如何在实际编程中使用这些系统调用，以及在开发网络应用程序时可能遇到的问题和解决方案。通过实例代码和清晰的解释，它帮助读者理解和掌握网络编程的基础知识，是学习Linux网络编程的重要参考资料。

资源详情

资源推荐

9 Beej’s Guide to Network Programming Using Internet Sockets

Actually, there’s a cleaner interface you can use instead of inet_addr(): it’s called

inet_aton() (“aton” means “ascii to network”):

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

int inet_aton(const char *cp, struct in_addr *inp);

And here’s a sample usage, while packing a struct sockaddr_in (this example will make

more sense to you when you get to the sections on bind() and connect().)

struct sockaddr_in my_addr;

my_addr.sin_family = AF_INET; // host byte order

my_addr.sin_port = htons(MYPORT); // short, network byte order

inet_aton("10.12.110.57", &(my_addr.sin_addr));

memset(&(my_addr.sin_zero), ’\0’, 8); // zero the rest of the struct

inet_aton(), unlike practically every other socket-related function, returns non-zero on

success, and zero on failure. And the address is passed back in inp.

Unfortunately, not all platforms implement inet_aton() so, although its use is preferred,

the older more common inet_addr() is used in this guide.

All right, now you can convert string IP addresses to their binary representations. What

about the other way around? What if you have a struct in_addr and you want to print it in

numbers-and-dots notation? In this case, you’ll want to use the function inet_ntoa() (“ntoa”

means “network to ascii”) like this:

printf("%s", inet_ntoa(ina.sin_addr));

That will print the IP address. Note that inet_ntoa() takes a struct in_addr as an

argument, not a long. Also notice that it returns a pointer to a char. This points to a statically

stored char array within inet_ntoa() so that each time you call inet_ntoa() it will overwrite

the last IP address you asked for. For example:

char *a1, *a2;

a1 = inet_ntoa(ina1.sin_addr); // this is 192.168.4.14

a2 = inet_ntoa(ina2.sin_addr); // this is 10.12.110.57

printf("address 1: %s\n",a1);

printf("address 2: %s\n",a2);

will print:

address 1: 10.12.110.57

address 2: 10.12.110.57

If you need to save the address, strcpy() it to your own character array.

That’s all on this topic for now. Later, you’ll learn to convert a string like “whitehouse.gov”

into its corresponding IP address (see DNS, below.)

3.2.1: Private (Or Disconnected) Networks

Lots of places have a ﬁrewall that hides the network from the rest of the world for their

own protection. And often times, the ﬁrewall translates “internal” IP addresses to “external”

(that everyone else in the world knows) IP addresses using a process called Network Address

Translation, or NAT.

Are you getting nervous yet? “Where’s he going with all this weird stuff?”

11 Beej’s Guide to Network Programming Using Internet Sockets

4. System Calls or Bust

This is the section where we get into the system calls that allow you to access the network

functionality of a Unix box. When you call one of these functions, the kernel takes over and

does all the work for you automagically.

The place most people get stuck around here is what order to call these things in. In that, the

man pages are no use, as you’ve probably discovered. Well, to help with that dreadful situation,

I’ve tried to lay out the system calls in the following sections in exactly (approximately) the

same order that you’ll need to call them in your programs.

That, coupled with a few pieces of sample code here and there, some milk and cookies

(which I fear you will have to supply yourself), and some raw guts and courage, and you’ll be

beaming data around the Internet like the Son of Jon Postel!

4.1. socket()–Get the File Descriptor!

I guess I can put it off no longer–I have to talk about the socket() system call. Here’s the

breakdown:

#include <sys/types.h>

#include <sys/socket.h>

int socket(int domain, int type, int protocol);

But what are these arguments? First, domain should be set to “PF_INET”. Next, the type

argument tells the kernel what kind of socket this is: SOCK_STREAM or SOCK_DGRAM. Finally, just

set protocol to “0” to have socket() choose the correct protocol based on the type. (Notes:

there are many more domains than I’ve listed. There are many more types than I’ve listed. See

the socket() man page. Also, there’s a “better” way to get the protocol, but specifying 0

works in 99.9% of all cases. See the getprotobyname() man page if you’re curious.)

socket() simply returns to you a socket descriptor that you can use in later system calls, or

-1 on error. The global variable errno is set to the error’s value (see the perror() man page.)

(This PF_INET thing is a close relative of the AF_INET that you used when initializing the

sin_family ﬁeld in your struct sockaddr_in. In fact, they’re so closely related that they

actually have the same value, and many programmers will call socket() and pass AF_INET as

the ﬁrst argument instead of PF_INET. Now, get some milk and cookies, because it’s times for a

story. Once upon a time, a long time ago, it was thought that maybe a address family (what the

“AF” in “AF_INET” stands for) might support several protocols that were referred to by their

protocol family (what the “PF” in “PF_INET” stands for). That didn’t happen. And they all

lived happily ever after, The End. So the most correct thing to do is to use AF_INET in your

struct sockaddr_in and PF_INET in your call to socket().)

Fine, ﬁne, ﬁne, but what good is this socket? The answer is that it’s really no good by itself,

and you need to read on and make more system calls for it to make any sense.

4.2. bind()–What port am I on?

Once you have a socket, you might have to associate that socket with a port on your local

machine. (This is commonly done if you’re going to listen() for incoming connections on a

speciﬁc port–MUDs do this when they tell you to “telnet to x.y.z port 6969”.) The port number

is used by the kernel to match an incoming packet to a certain process’s socket descriptor. If

you’re going to only be doing a connect(), this may be unnecessary. Read it anyway, just for

kicks.

Here is the synopsis for the bind() system call:

#include <sys/types.h>

#include <sys/socket.h>

Beej’s Guide to Network Programming Using Internet Sockets 12

int bind(int sockfd, struct sockaddr *my_addr, int addrlen);

sockfd is the socket ﬁle descriptor returned by socket(). my_addr is a pointer to a

struct sockaddr that contains information about your address, namely, port and IP address.

addrlen can be set to sizeof(struct sockaddr).

Whew. That’s a bit to absorb in one chunk. Let’s have an example:

#include <string.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#define MYPORT 3490

main()

{

int sockfd;

struct sockaddr_in my_addr;

sockfd = socket(PF_INET, SOCK_STREAM, 0); // do some error checking!

my_addr.sin_family = AF_INET; // host byte order

my_addr.sin_port = htons(MYPORT); // short, network byte order

my_addr.sin_addr.s_addr = inet_addr("10.12.110.57");

memset(&(my_addr.sin_zero), ’\0’, 8); // zero the rest of the struct

// don’t forget your error checking for bind():

bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr));

There are a few things to notice here: my_addr.sin_port is in Network Byte Order. So

is my_addr.sin_addr.s_addr. Another thing to watch out for is that the header ﬁles might

differ from system to system. To be sure, you should check your local man pages.

Lastly, on the topic of bind(), I should mention that some of the process of getting your

own IP address and/or port can be automated:

my_addr.sin_port = 0; // choose an unused port at random

my_addr.sin_addr.s_addr = INADDR_ANY; // use my IP address

See, by setting my_addr.sin_port to zero, you are telling bind() to choose the port for

you. Likewise, by setting my_addr.sin_addr.s_addr to INADDR_ANY, you are telling it to

automatically ﬁll in the IP address of the machine the process is running on.

If you are into noticing little things, you might have seen that I didn’t put INADDR_ANY into

Network Byte Order! Naughty me. However, I have inside info: INADDR_ANY is really zero!

Zero still has zero on bits even if you rearrange the bytes. However, purists will point out that

there could be a parallel dimension where INADDR_ANY is, say, 12 and that my code won’t work

there. That’s ok with me:

my_addr.sin_port = htons(0); // choose an unused port at random

my_addr.sin_addr.s_addr = htonl(INADDR_ANY); // use my IP address

Now we’re so portable you probably wouldn’t believe it. I just wanted to point that out,

since most of the code you come across won’t bother running INADDR_ANY through htonl().

bind() also returns -1 on error and sets errno to the error’s value.

Another thing to watch out for when calling bind(): don’t go underboard with your port

numbers. All ports below 1024 are RESERVED (unless you’re the superuser)! You can have

any port number above that, right up to 65535 (provided they aren’t already being used by

another program.)

剩余72页未读，继续阅读

hwmike

粉丝: 0
资源: 5

Beej的互联网套接字网络编程指南

Beej的使用Internet套接字的网络编程指南Beej's Guide to Network Programming Using Internet Sockets

Beej's Guide to Network Programming Using Internet Sockets

c++ socket学习网站

介绍一下C++如何通讯

socket的参考文献

java基于SpringBoot+vue 美食信息推荐系统源码 带毕业论文

Sigrity-SystemSI-Statistical Analysis Application Note.rar

MATLAB的汉字定位检测识别系统GUI设计.zip

Sigrity-T2B Quick Reference.rar

仿ios音量调节的效果.zip

手机通讯集信息,文件,语音呼叫于一体(小鸟版).zip

疫苗接种管理系统 基于Springboot和Mysql的疫苗接种管理系统代码 ，包括程序，中文注释，配置说明操作步骤

java基于SpringBoot+vue 校园疫情防控管理系统源码 带毕业论文

基于springboot的医院信管系统设计与实现.docx

java基于ssm+jsp二手手机回收平台管理系统源码 带毕业论文+PPT

ssm+mysql的银发在线教育云平台(源码+lw+ppt)

java基于SpringBoot+vue 进销存系统系统源码 带毕业论文

基于SpringBoot的博客系统.zip

基于android北京地铁小助手有导航功能.zip

电子杂志（带翻页效果）.zip

最新资源

java基于SpringBoot+vue 美食信息推荐系统源码带毕业论文

疫苗接种管理系统基于Springboot和Mysql的疫苗接种管理系统代码，包括程序，中文注释，配置说明操作步骤

java基于SpringBoot+vue 校园疫情防控管理系统源码带毕业论文

java基于ssm+jsp二手手机回收平台管理系统源码带毕业论文+PPT

java基于SpringBoot+vue 进销存系统系统源码带毕业论文