大致流程：
建立一个client端，一个server端，自己构建IP头和UDP头，写入数据(hello,world!)后通过原始套接字(SOCK_RAW)将包发出去。
server端收到数据后，打印UDP数据并发送确认消息(yes)，client收到yes后将其打印。
其中：
client端IP：192.168.11.104 端口：8600
server端IP：192.168.11.105 端口：8686
注意事项：
1.运行原始套接字socket需要有root权限。
2.注意主机字节序和网络字节序的转
实现如下：
client端：
1 /*
2 ============================================================================
3 Name : test_client.c
4 Author : huh
5 Version :
6 Copyright : ---notice---
7 Description : Hello World in C, Ansi-style
8 ============================================================================
9 */
10
11 #include <sys/types.h>
12 #include <sys/socket.h>
13 #include <stdio.h>
14 #include <netinet/in.h>
15 #include <arpa/inet.h>
16 #include <unistd.h>
17 #include <stdlib.h>
18 #include <string.h>
19 #include <netinet/ip_icmp.h>
20 #include <netinet/udp.h>
21
22 #define MAXLINE 1024*10
23
24 struct udp_front //udp
25 {
26 uint32_t srcip;
27 uint32_t desip;
28 u_int8_t zero;
29 u_int8_t protocol;
30 u_int16_t len;
31 };
32
33 u_int16_t in_chksum(u_int16_t *addr, int len);
34 u_int16_t udp_check(char *sendbuf, int len, const struct udp_front front);
35 int make_message(char sendbuf[], int send_buf_len, uint32_t src_ip, u_int16_t src_port, uint32_t des_ip, u_int16_t des_port);
36
37 int main()
38 {
39 int raw_sockfd;
40 int size = 1024*50;
41 char send_message[MAXLINE];
42 struct sockaddr_in server_address;
43 //创建原始套接字
44 raw_sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
45 //创建套接字地址
46 bzero(&server_address,sizeof(server_address));
47 server_address.sin_family = AF_INET;
48 server_address.sin_addr.s_addr = inet_addr("192.168.11.105");
49 //设置套接字为随数据包含IP首部(设置这个选项后需要我们手动写入IP头)
50 setsockopt(raw_sockfd, IPPROTO_IP, IP_HDRINCL, &size, sizeof(size));
51
52 int len;
53 bzero(&send_message, sizeof(send_message));
54 //拼接完整的UDP数据包(IP头+UDP头+数据)
55 int mesg_len = make_message(send_message, MAXLINE, inet_addr("192.168.11.104"), 8600, inet_addr("192.168.11.105"), 8686);
56 //将IP数据包发送出去
57 sendto(raw_sockfd, send_message, mesg_len, 0, (struct sockaddr *)&server_address, sizeof(server_address));
58 close(raw_sockfd);
59 //
60 //下面我们开始接受服务器返回的包
61 int client_sockfd;
62 int server_len;
63 char recv_message[MAXLINE];
64 struct sockaddr_in server_addr;
65 client_sockfd = socket(AF_INET, SOCK_DGRAM, 0);
66 server_addr.sin_family = AF_INET;
67 server_addr.sin_addr.s_addr = inet_addr("192.168.11.104");
68 server_addr.sin_port = htons(8600);
69 server_len = sizeof(server_address);
70 bind(client_sockfd, (struct sockaddr *)&server_addr, server_len);
71
72 bzero(&recv_message, sizeof(recv_message));
73 len = recvfrom(client_sockfd, recv_message, MAXLINE, 0, NULL, NULL);
74 printf("收到的应答：%s\n",recv_message);
75 return 0;
76 }
77
78 //拼接IP数据报
79 int make_message(char sendbuf[], int send_buf_len, uint32_t src_ip, u_int16_t src_port, uint32_t des_ip, u_int16_t des_port)
80 {
81 char message[1005];
82 bzero(message, sizeof(message));
83 strcpy(message,"hello,world!");
84 printf("message len:%d\n",strlen(message));
85 struct iphdr *ip;
86 ip = (struct iphdr *)sendbuf;
87 ip->ihl = sizeof(struct iphdr) >> 2; //首部长度
88 ip->version = 4; //ip协议版本
89 ip->tos = 0; //服务类型字段
90 ip->tot_len = 0; //总长度
91 ip->id = 1000; //
92 ip->frag_off = 0;
93 ip->ttl = 128;
94 ip->protocol = IPPROTO_UDP;
95 ip->check = 0; //内核会算相应的效验和
96 ip->saddr = src_ip;
97 ip->daddr = des_ip;
98
99 struct udp_front front;
100 front.srcip = src_ip;
101 front.desip = des_ip;
102 front.len = htons(8+strlen(message));
103 front.protocol = 17;
104 front.zero = 0;
105
106 struct udphdr *udp;
107 udp = (struct udphdr *)(sendbuf + sizeof(struct iphdr));
108 udp->source = htons(src_port); //源端口
109 udp->dest = htons(des_port); //目的端口
110 udp->check = 0; //效验和，效验整个udp数据报
111 strcpy((sendbuf+20+8), message);
112 udp->len = htons(8+strlen(message)); //udp数据报总长度
113
114 udp->check = udp_check((sendbuf+20), 8+strlen(message), front);
115
116 ip->tot_len = (20 + 8 + strlen(message)); //总长度
117 printf("ip->tot_len:%d\n",ip->tot_len);
118 ip->check = in_chksum((unsigned short *)sendbuf, 20);
119
120 return (ip->tot_len);
121 }
122
123 //计算udp效验和
124 unsigned short udp_check(char *sendbuf, int len, const struct udp_front front)
125 {
126 char str[MAXLINE];
127 bzero(&str, MAXLINE);
128 bcopy(&front, str, sizeof(front));
129 bcopy(sendbuf, str+sizeof(front), len);
130 struct udp_front *ptr;
131 ptr = (struct udp_front *)str;
132 char *s;
133 s = (str+20);
134 return in_chksum((unsigned short *)str, sizeof(front)+len);
135 }
136
137 //效验和算法
138 uint16_t in_chksum(uint16_t *addr, int len)
139 {
140 int nleft = len;
141 uint32_t sum = 0;
142 uint16_t *w = addr;
143 uint16_t answer = 0;
144 //把ICMP报头二进制数据以2字节为单位累加起来
145 while (nleft > 1)
146 {
147 sum += *w++;
148 nleft -= 2;
149 }
150 if (nleft == 1)
151 {
152 *(unsigned char *)(&answer) = *(unsigned char *)w;
153 sum += answer;
154 }
155 sum = (sum>>16) + (sum&0xffff);
156 sum += (sum>>16);
157 answer = ~sum;
158 return answer;
159 }
server端：
1 /*
2 ============================================================================
3 Name : test_server.c
4 Author : huh
5 Version :
6 Copyright : ---notice---
7 Description : Hello World in C, Ansi-style
8 ============================================================================
9 */
10
11 #include <sys/types.h>
12 #include <sys/socket.h>
13 #include <stdio.h>
14 #include <netinet/in.h>
15 #include <arpa/inet.h>
16 #include <unistd.h>
17 #include <stdlib.h>
18 #include <string.h>
19
20 #define MAXLINE 1024*50
21
22 int main()
23 {
24 int server_sockfd;
25 int server_len, client_len;
26 struct sockaddr_in server_address;
27 struct sockaddr_in client_address;
28
29 server_sockfd = socket(AF_INET, SOCK_DGRAM, 0);
30
31 server_address.sin_family = AF_INET;
32 server_address.sin_addr.s_addr = inet_addr("192.168.11.105");
33 server_address.sin_port = htons(8686);
34
35 server_len = sizeof(server_address);
36 bind(server_sockfd, (struct sockaddr *)&server_address, server_len);
37
38 for( ; ; )
39 {
40 int len;
41 char recv_mesg[MAXLINE];
42 char send_mesg[20];
43 client_len = sizeof(struct sockaddr_in);
44 printf("server2 waiting!\n");
45 len = recvfrom(server_sockfd, recv_mesg, MAXLINE, 0, (struct sockaddr *) &client_address, (socklen_t *) &client_len);
46 printf("收到包的长度为:%d\n",len);
47 printf("%s\n",recv_mesg);
48 strcpy(send_mesg,"yes");
49 sendto(server_sockfd, send_mesg, strlen(send_mesg), 0, (struct sockaddr *) &client_address, client_len); //将包发出去
50 ;
51 }
52 return 0;
53 }
时间： 2024-12-20 09:11:54