《网络编程技术》实验指导书(8)

if(pthread_create(&tid, NULL, start_routine, (void *)arg)) {

perror(\ error.\\n\ exit(-1); } }

close(listenfd); }

static pthread_key_t key;

static pthread_once_t once = PTHREAD_ONCE_INIT; struct DATA_THR { int index; };

static void key_destroy(void *buf) { free(buf); }

static void buffer_key_alloc() {

pthread_key_create(&key, key_destroy); }

void savedata(char *recvbuf, int len, char *cli_data) {

struct DATA_THR *data;

pthread_once(&once, buffer_key_alloc);

if ((data = (struct DATA_THR *)pthread_getspecific ( key )) == NULL) { data = (struct DATA_THR *) calloc (1, sizeof(struct DATA_THR)); pthread_setspecific (key, data); data -> index = 0; }

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int i;

for (i=0; iindex++] = recvbuf[i]; cli_data[data->index] = '\\0'; }

void process_client(int connectfd,struct sockaddr_in client){ char recvbuf[MAXCHARSIZE]; char sendbuf[MAXCHARSIZE]; char client_name[MAXCHARSIZE]; char client_data[5000]; int recvlen,i;

printf(\ send(connectfd,\ recvlen=recv(connectfd,client_name,MAXCHARSIZE,0); if(recvlen==0){ close(connectfd);

printf(\ return; }

else if(recvlen<0){ close(connectfd);

printf(\ return; }

client_name[recvlen]='\\0';

printf(\ bzero(recvbuf,1000);

while(recvlen=recv(connectfd,recvbuf,MAXCHARSIZE,0)){ savedata(recvbuf,recvlen,client_data); recvbuf[recvlen]='\\0';

printf(\ message:%s\\n\

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for(i=0;i

send(connectfd,sendbuf,strlen(sendbuf),0);

bzero(recvbuf,1000); } /*while*/

printf(\ close(connectfd); }

void *start_routine(void *arg) { struct ARG *info; info = (struct ARG *)arg;

process_client(info -> connfd, info -> client); free(arg);

pthread_exit(NULL); }

\\n\38

实验六 实现NTP网络授时客户端

1． 实验目的

1．利用UDP协议实现NTP网络授时服务器； 2．使用select在NTP客户端中实现I/O复用； 2． 实验要求

1．认真阅读和掌握本实验的相关的知识点。 2．上机编写并运行本程序。

3．保存和打印出程序的运行结果，并结合程序进行分析。 3． 实验内容

1、阅读NTP协议，使用UDP连接NTP服务器，构建NTP协议包，向服务器发送客户数据，发送成功后显示发送数量，接收服务端的返回信息，要求客户端具有多路I/O复用的能力。只在数据接受完毕后读取数据。

2、根据NTP协议解析服务器返回的信息，从中获得服务器的准确时间，然后更新本地系统时间。 4. 实验内容程序 程序源代码：

/*

* ntp_client_by_other_main.c *

* Created on: 2010-9-8 * Author: kerwin */

#include #include #include

#include #include #include #include #include #include

#define NTP_SERVER \#define NTP_PORT 123

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//

//rfc1305 defined from 1900 so also 2208988800 (1900 - 1970 ) seconds left //

//timeval.tv_sec + JAN_1970 = timestamp.coarse #define JAN_1970 0x83aa7e80

//timeval.tv_usec=>timestamp.fine

#define NTPFRAC(x) (4294 * (x) + ((1981 * (x))>>11)) //timeval.tv_usec<=timestamp.fine

#define USEC(x) (((x) >> 12) - 759 * ((((x) >> 10) + 32768) >> 16))

#define Data(i) ntohl(((unsigned int *)data)[i])

#define LI 0 #define VN 3 #define MODE 3 #define STRATUM 0 #define POLL 4 #define PREC -6

struct ntptime {

unsigned int coarse; unsigned int fine; };

void send_packet(int fd) { unsigned int data[12]; struct timeval now; int ret;

if (sizeof(data) != 48) {

fprintf(stderr, \ return; }

memset((char*) data, 0, sizeof(data));

data[0] = htonl((LI << 30) | (VN << 27) | (MODE << 24) | (STRATUM << 16) | (POLL << 8) | (PREC & 0xff));

data[1] = htonl(1 << 16); /* Root Delay (seconds) */

data[2] = htonl(1 << 16); /* Root Dispersion (seconds) */ gettimeofday(&now, NULL);

data[10] = htonl(now.tv_sec + JAN_1970); /* Transmit Timestamp coarse */ data[11] = htonl(NTPFRAC(now.tv_usec)); /* Transmit Timestamp fine */

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