unix网络编程笔记---14.UDP的C/S之1回射

一.
1. 流程描述
udp的demo既有server端又有client端，两者互相通信
client --> sendto    --> recvfrom
server--> recvfrom --> sendto

---

2. 代码
2.1 client.c

cong@msi:/work/test/tcpip/14udp/client$ cat client.c
#include "utils.h"

//#define TIME_SERV_ADDR "192.168.4.98"
#define TIME_SERV_ADDR "127.0.0.1"

void dg_cli(FILE* fp, int sockfd, const struct sockaddr* pservaddr, socklen_t servlen)
{
    int n;
    char sendline[MAXLINE], recvline[MAXLINE];
    while(fgets(sendline, MAXLINE, fp) != NULL)
    {
        //write(sockfd, sendline, strlen(sendline));
        //这儿的pservaddr一定要初始化，要不client就不知道要发给谁了
        sendto(sockfd, sendline, strlen(sendline), 0, pservaddr, servlen); //a.sendto发送到服务器
        //这儿的第5个参数设为NULL,因为client不需要知道是谁发给它的,所以书上说这儿有个bug
        n = recvfrom(sockfd, recvline, MAXLINE, 0, NULL, NULL);            //d.recvfrom接收服务器的数据
        recvline[n] = 0;
        fputs(recvline, stdout);
    }
}

int main ( int argc, char *argv[] )
{
    int sockfd, n;
    struct sockaddr_in servaddr;
    char recvline[1024];
    //sockfd = socket(AF_INET, SOCK_STREAM, 0);
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if(sockfd < 0)
        return -1;
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(13999);
    inet_pton(AF_INET, TIME_SERV_ADDR, &servaddr.sin_addr);

    //connect(sockfd, (const struct sockaddr*)&servaddr, sizeof(servaddr));
    dbmsg("next dg_cli");
    dg_cli(stdin, sockfd, (const struct sockaddr*)&servaddr, sizeof(servaddr));
    return EXIT_SUCCESS;
}

2.2 serv.c

cong@msi:/work/test/tcpip/14udp/serv$ cat udpserv.c
#include "utils.h"

void dg_echo(int sockfd, struct sockaddr* pcliaddr, socklen_t clilen)
{
    int n;
    socklen_t len;
    char mesg[MAXLINE];
    while(1)
    {
        len = clilen;
        //recvfrom把client的端口号与地址保存在pcliaddr中
        n = recvfrom(sockfd, mesg, MAXLINE, 0, pcliaddr, &len);  //b.recvfrom收到client的数据
        //因为recvfrom己保存了client的端口与地址，所以serv就知道该发到哪儿去了,这就是pcliaddr的作用
        sendto(sockfd, mesg, n, 0, pcliaddr, len);               //c.sendto发送到client
    }
}

int main ( int argc, char *argv[] )
{
    int sockfd, connfd;
    struct sockaddr_in servaddr, cliaddr;
    pid_t childpid;
    char buf[1024];
    int len;
    //sockfd = socket(AF_INET, SOCK_STREAM, 0);
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);    //由SOCK_STREAM改为SOCK_DGRAM
    if(sockfd < 0)
        return -1;
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(13999);
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    //inet_pton(AF_INET, TIME_SERV_ADDR, &servaddr.sin_addr);

    bind(sockfd, (const struct sockaddr*)&servaddr, sizeof(servaddr)); //bind就行了没有listen
    dg_echo(sockfd, (struct sockaddr*)&cliaddr, sizeof(cliaddr));

    return EXIT_SUCCESS;
}

这儿打印了pcliaddr

在内核的include/linux/socket.h中
struct sockaddr {
    sa_family_t sa_family; /* address family, AF_xxx */
    char sa_data[14]; /* 14 bytes of protocol address */
};

所以打印如下:
for(i=0; i<14; i++)
    dbmsg("%d= 0x%x",i, (unsigned char)pcliaddr->sa_data[i]);

udpserv.c:dg_echo[16]: 0= 0xb5
udpserv.c:dg_echo[16]: 1= 0xba
udpserv.c:dg_echo[16]: 2= 0x7f
udpserv.c:dg_echo[16]: 3= 0x0
udpserv.c:dg_echo[16]: 4= 0x0
udpserv.c:dg_echo[16]: 5= 0x1
udpserv.c:dg_echo[16]: 6= 0x0
udpserv.c:dg_echo[16]: 7= 0x0
udpserv.c:dg_echo[16]: 8= 0x0
udpserv.c:dg_echo[16]: 9= 0x0
udpserv.c:dg_echo[16]: 10= 0x0
udpserv.c:dg_echo[16]: 11= 0x0
udpserv.c:dg_echo[16]: 12= 0x0
udpserv.c:dg_echo[16]: 13= 0x0
其中 0xb5 0xba = b5ba=46522 --> client的端口号
     7f 00 00 01--> 127.0.0.1 --> client的地址

2.3
client.rar (下载后改名为client.tar.gz)
serv.rar (下载后改名为serv.tar.gz)

---

二. 修改版
1. clinet.c

cong@msi:/work/test/tcpip/16udp/client$ cat udpclient.c
#include "utils.h"
#include <unistd.h>
#include <sys/time.h>
#include <stdlib.h>

//#define TIME_SERV_ADDR "192.168.4.98"
#define TIME_SERV_ADDR "127.0.0.1"

long int get_now_us_time()
{
    struct timeval start;
    long int now_time;
    gettimeofday(&start, NULL);
    now_time = start.tv_sec*1000+ start.tv_usec/1000;
    return now_time;
}


void dg_cli(FILE* fp, int sockfd, const struct sockaddr* pservaddr, socklen_t servlen)
{
    int n, i,j;
    long int t1,t2;
    char sendline[MAXLINE], recvline[MAXLINE];
    //while(fgets(sendline, MAXLINE, fp) != NULL)
    //while(1)
    for(j=0; j<3; j++)
    {
        memset(sendline, 0, sizeof(sendline));
        for(i=0; i<64; i++)
        {
            sendline[i] = i;
        }
        t1 = get_now_us_time();
        //write(sockfd, sendline, strlen(sendline));
        sendto(sockfd, sendline, 64, 0, pservaddr, servlen);

        n = recvfrom(sockfd, recvline, MAXLINE, 0, NULL, NULL);
        t2 = get_now_us_time();
        printf("time=%ld\n", t2-t1);
        recvline[n] = 0;
        fputs(recvline, stdout);
        sleep(1);
    }

}

int main ( int argc, char *argv[] )
{
    int sockfd, n;
    struct sockaddr_in servaddr;
    char recvline[1024];
    //sockfd = socket(AF_INET, SOCK_STREAM, 0);
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if(sockfd < 0)
        return -1;
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(9000);
    inet_pton(AF_INET, TIME_SERV_ADDR, &servaddr.sin_addr);

    //connect(sockfd, (const struct sockaddr*)&servaddr, sizeof(servaddr));
    dbmsg("next dg_cli");
    dg_cli(stdin, sockfd, (const struct sockaddr*)&servaddr, sizeof(servaddr));
    return EXIT_SUCCESS;
}

2.server

cong@msi:/work/test/tcpip/16udp/serv$ cat udpserv.c
#include "utils.h"

char * sock_ntop(const struct sockaddr *sa, socklen_t salen)
{
    char        portstr[8];
    static char str[128]; /* Unix domain is largest */
    struct sockaddr_in *sin = (struct sockaddr_in *) sa;
    //only process AF_INET
    if (inet_ntop(AF_INET, &sin->sin_addr, str, sizeof(str)) == NULL)
        return(NULL);
    if (ntohs(sin->sin_port) != 0) {
        snprintf(portstr, sizeof(portstr), ":%d", ntohs(sin->sin_port));
        strcat(str, portstr);
    }
    return(str);
}

void dg_echo(int sockfd, struct sockaddr* pcliaddr, socklen_t clilen)
{
    int n;
    int i;
    socklen_t len;
    char mesg[MAXLINE];
    while(1)
    {
        len = clilen;
    #if 0
        for(i=0; i<14; i++)
            dbmsg("%d= 0x%x",i, (unsigned char)pcliaddr->sa_data[i]);
    #endif
        n = recvfrom(sockfd, mesg, MAXLINE, 0, pcliaddr, &len);
        dbmsg("n=%d, len=%d", n, len);
        for(i=0; i<n; i++)
            printf("%d=0x%x ",i, mesg[i]);
        printf("\n");
        sendto(sockfd, mesg, n, 0, pcliaddr, len);
    }
}

int main ( int argc, char *argv[] )
{
    int sockfd, connfd;
    struct sockaddr_in servaddr, cliaddr;
    pid_t childpid;
    char buf[1024];
    int len;
    //sockfd = socket(AF_INET, SOCK_STREAM, 0);
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if(sockfd < 0)
        return -1;
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(9000);
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    //inet_pton(AF_INET, TIME_SERV_ADDR, &servaddr.sin_addr);

    bind(sockfd, (const struct sockaddr*)&servaddr, sizeof(servaddr));
    dg_echo(sockfd, (struct sockaddr*)&cliaddr, sizeof(cliaddr));

    return EXIT_SUCCESS;
}

2.3
client.rar(下载后改名为client.tar.gz)
serv.rar(下载后改名为serv.tar.gz)