socket编程实战

其他 2021-03-06 15:32:39 阅读次数: 0

socket编程实战

一、TCP三次握手&四次握手

1. tcp三次握手与四次握手简介

tcp三次握手

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tcp四次握手

在这里插入图片描述

2. 在win10中打开cmd命令行窗口，用telnet进入金庸游戏

telnet（进入telnet客户端）->set localecho（打开本地回显）->open 10.1.230.41 3900（进入游戏服务器）

3. 查看当前网络ip

cmd->ipconfig

在这里插入图片描述

4. 查看三次握手

wireshark抓取了很多的数据包，我们用过滤器进行筛选
tcp.port == 3900

在这里插入图片描述

5. 断开游戏服务器并分析四次握手的包

在这里插入图片描述

二、原始套接字编程&SOCKET应用

1.Teardrop代码编程

实验代码
代码为“网络编程技术”参考书上 “2.11 原始套接字编程”中的Teardrop代码编程

#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
/* OpenBSD < 2.1, all FreeBSD and netBSD, BSDi < 3.0 */
#define FIX(n)  (n)
#else  
/* OpenBSD 2.1, all Linux */
#define FIX(n)  htons(n)
#endif  /* STRANGE_BSD_BYTE_ORDERING_THING */

#define IP_MF 0x2000  /* More IP fragment en route */
#define IPH 0x14    /* IP header size */
#define UDPH 0x8     /* UDP header size */
#define PADDING  0x1c    /* datagram frame padding for first packet */
#define MAGIC  0x3     /* Magic Fragment Constant (tm).  Should be 2 or 3 */
#define COUNT 0x1      /* Linux dies with 1, NT is more stalwart and can
                        * withstand maybe 5 or 10 sometimes...  Experiment.*/
                    

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;
    // 定义源地址和目的地址
    u_long src_ip = 0, dst_ip = 0;
    // 定义源端口和目的端口
    u_short src_prt = 0, dst_prt = 0;
    // 定义一个32位的IPv4地址
    struct in_addr addr;
    printf("teardrop route|daemon9\n\n");
    //创建原始套接字
    if((rip_sock = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
    {
    
    
        fprintf(stderr, "raw socket");
        exit(1);
    }
    //设置套接字选项IP_HDRINCL
    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]);
    // 设置源IP 和 目的IP
    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);
}


// 设置 IP 包的内容
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
    // 套接字地址结构
    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);
}

编译及运行

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在这里插入图片描述

抓包结果
在这里插入图片描述

2.SOCKET应用实例

服务器

#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: 
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; 
	}
// loop through all the results and bind to the first we can 
    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(&sa.sa_mask); 
    sa.sa_flags = SA_RESTART; 
    if (sigaction(SIGCHLD, &sa, NULL) == -1) {
    
     
        perror("sigaction"); 
        exit(1); 
    }
    printf("server: waiting for connections...\n"); 
    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 
            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

#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

//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);
}

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;
	}
    // loop through all the results and connect to the first we can 
	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);// 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;
}

编译文件

#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"  //port we're listening on

//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);
}

int main(void)
{
    
    
    fd_set master; 
    // master file descriptor list 
    fd_set read_fds; // temp file descriptor list for select() 
    int fdmax; 
    // maximum file descriptor number
    int listener; 
    // listening socket descriptor 
    int newfd; 
    // newly accept()ed socket descriptor 
    struct sockaddr_storage remoteaddr; // client address 
    socklen_t addrlen; 
    char buf[256]; 
    // buffer for client data 
    int nbytes; 
    char remoteIP[INET6_ADDRSTRLEN]; 
    int yes=1; 
    // for setsockopt() SO_REUSEADDR, below 
    int i, j, rv; 
    struct addrinfo hints, *ai, *p; 
    FD_ZERO(&master); 
    // clear the master and temp sets 
    FD_ZERO(&read_fds); 
    // get us a socket and bind it 
    memset(&hints, 0, sizeof hints); 
    hints.ai_family = AF_UNSPEC; 
    hints.ai_socktype = SOCK_STREAM; 
    hints.ai_flags = AI_PASSIVE; 
    if((rv = getaddrinfo(NULL, PORT, &hints, &ai)) != 0)
    {
    
    
        fprintf(stderr, "selectserver:%s\n", gai_strerror(rv));
        exit(1);
    }

    for(p = ai; p != NULL; p = p->ai_next)
    {
    
    
        listener = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
        if(listener < 0)
        {
    
    
            continue;
        }
        // lose the pesky "address already in use" error message 
        setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));
        if(bind(listener, p->ai_addr, p->ai_addrlen) < 0)
        {
    
    
            close(listener);
            continue;
        }
        break;
    }
	// if we got here, it means we didn't get bound 
    if(p == NULL)
    {
    
    
        fprintf(stderr, "selectserver:failed to bind\n");
        exit(2);
    }

    freeaddrinfo(ai);  // all done with this 
    // listen
    if(listen(listener, 10) == -1)
    {
    
    
        perror("listen");
        exit(3);
    }
    // add the listener to the master set 
    FD_SET(listener, &master);
	// keep track of the biggest file descriptor 
    fdmax = listener;  // so far, it's this one 
	// main loop 
    for(;;)
    {
    
    
        read_fds = master; // copy it 
        if(select(fdmax + 1, &read_fds, NULL, NULL, NULL) == -1)
        {
    
    
            perror("select");
            exit(4);
        }
		// run through the existing connections looking for data to read 
        for(i = 0; i <= fdmax; i++)
        {
    
    
            if(FD_ISSET(i, &read_fds))// we got one!!
            {
    
    
                if(i == listener)
                {
    
    
                    // handle new connections
                    addrlen = sizeof remoteaddr;
                    newfd = accept(listener, (struct sockaddr *)&remoteaddr, &addrlen);

                    if(newfd == -1)
                    {
    
    
                        perror("accept");
                    }
                    else
                    {
    
    
                        FD_SET(newfd, &master); // add to master set 
                        if(newfd > fdmax)
                        {
    
    
                            // keep track of the max 
                            fdmax = newfd;
                        }
                        printf("selectserver: new connection from %s on " 
                        "socket %d\n", 
                        inet_ntop(remoteaddr.ss_family, 
                        get_in_addr((struct sockaddr*)&remoteaddr), 
                        remoteIP, INET6_ADDRSTRLEN), 
                        newfd); 
                    }
                }
                else
                {
    
    
                    // handle data from a client 
                    if((nbytes = recv(i, buf, sizeof buf, 0)) <= 0)
                    {
    
    
                        // got error or connection closed by client 
                        if(nbytes == 0)
                        {
    
    
                            // connection closed 
                            printf("selectserver:socket %d hung up\n", i);
                        }
                        else
                        {
    
    
                            perror("recv");
                        }
                        close(i);// bye! 
                        FD_CLR(i, &master);// remove from master set 
                    }
                    else
                    {
    
    
                        // we got some data from a client 
                        for(j =0; j <= fdmax; j++)
                        {
    
    
			    			// send to everyone! 
                            if(FD_ISSET(j, &master))
                            {
    
    
                                 // except the listener and ourselves 
                                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;
}

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