C语言udp协议，局域网下，这两段代码为什么不能通讯？

client.c 发送消息

#include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<errno.h>
#include<unistd.h>
#include<sys/wait.h>
#include<signal.h>
#include<stdio.h>
#include<string.h>
int main (void)
{
    int sock ;
    if((sock=socket(PF_INET,SOCK_DGRAM,0)) <0)
    {
        perror("socket");
        return 1 ;
    }
    struct sockaddr_in  servaddr;
    bzero(&servaddr,sizeof(servaddr));
    servaddr.sin_family =  AF_INET;
    servaddr.sin_port = htons(12345);
    servaddr.sin_addr.s_addr = inet_addr("192.168.0.104");

    char  str[4]="123";
    int i = 1;
    while (i++!= 100000000)
    {
        sendto(sock,str, sizeof(str), 0,(struct sockaddr *)&servaddr, sizeof(servaddr));
    }
    close(sock);

    return 0;
}

server.c收消息

 #include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<errno.h>
#include<unistd.h>
#include<sys/wait.h>
#include<signal.h>
#include<stdio.h>
#include<fcntl.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#include<time.h>
#define MAXBUF 1024
int main (void)
{
    int listener,kdpfd,nfds,n;
    socklen_t len;
    len = sizeof(struct sockaddr_in);
    struct sockaddr_in my_addr,peer_addr;
    clock_t start,finish;
    double time;
    if((listener=socket(PF_INET,SOCK_DGRAM,0))==-1)
    {
        perror(" socket ");
        exit(1);
    }
    int  opt=SO_REUSEADDR;
    if(setsockopt(listener,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt))==-1)
    {
        perror("setsockopt");
        exit(1);
    }
    bzero(&my_addr,sizeof(my_addr));
    my_addr.sin_family = AF_INET;
    my_addr.sin_port = htons(12345);
    my_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    if((bind(listener,(struct sockaddr *)&my_addr,sizeof (struct sockaddr))==-1))
    {
        perror("bind");
        exit(1);
    }
    int cnt;
    int i;
    for(i= 0 ;i<10;i++)
    {
        cnt = 0;
        start = clock();
        while(1)
        {
            recvfrom(listener,0,0,0,(struct sockaddr *)&peer_addr,&len);
            ++cnt;
            if(cnt == 100000)
                break;
        }
        finish = clock();
        time +=  (double)(finish - start)/CLOCKS_PER_SEC;
    }
    printf("%lf \n",time/10);
    close(listener);
    close(kdpfd);
    return 0;
}

每一步操作都检测一下返回值，看看是否有哪个api执行失败了，确定问题之后进行解决

其实碰到这样到问题，自己调试一下就可以了。并且setsockopt那个字段一般用于tcp，作为闲时可重用到
客户端：

 #include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<errno.h>
#include<unistd.h>
#include<sys/wait.h>
#include<signal.h>
#include<stdio.h>
#include<string.h>
int main (void)
{
    int sock ;
    if((sock=socket(PF_INET,SOCK_DGRAM,0)) <0)
    {
        perror("socket");
        return 1 ;
    }
    struct sockaddr_in  servaddr;
    bzero(&servaddr,sizeof(servaddr));
    servaddr.sin_family =  AF_INET;
    servaddr.sin_port = htons(12345);
    servaddr.sin_addr.s_addr = inet_addr("192.168.13.2");

    char  str[4]="123";
    int i = 0;
    while (i++!= 10)
    {
        sendto(sock,str, sizeof(str), 0,(struct sockaddr *)&servaddr, sizeof(servaddr));
    printf("sendto!\n");
    }
    close(sock);

    return 0;
}

服务器
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
int main (void)
{
int sock ;
if((sock=socket(PF_INET,SOCK_DGRAM,0)) <0)
{
perror("socket");
return 1 ;
}
struct sockaddr_in servaddr;
bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(12345);
servaddr.sin_addr.s_addr = inet_addr("192.168.13.2");

char  str[4]="123";
int i = 0;
while (i++!= 10)
{
    sendto(sock,str, sizeof(str), 0,(struct sockaddr *)&servaddr, sizeof(servaddr));
printf("sendto!\n");
}
close(sock);

return 0;

}

上面服务器代码弄到有问题：
服务器：

  #include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<errno.h>
#include<unistd.h>
#include<sys/wait.h>
#include<signal.h>
#include<stdio.h>
#include<fcntl.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#include<time.h>
#define MAXBUF 1024
int main (void)
{
    int listener,kdpfd,nfds,n;
    socklen_t len;
    char buf[100];
    len = sizeof(struct sockaddr_in);
    struct sockaddr_in my_addr,peer_addr;
    clock_t start,finish;
    double time;
    if((listener=socket(PF_INET,SOCK_DGRAM,0))<=-1)
    {
        perror(" socket ");
        exit(1);
    }
    int  opt=SO_REUSEADDR;
    if(setsockopt(listener,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt))==-1)
    {
        perror("setsockopt");
        exit(1);
    }
    bzero(&my_addr,sizeof(my_addr));
    my_addr.sin_family = AF_INET;
    my_addr.sin_port = htons(12345);
    my_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    if((bind(listener,(struct sockaddr *)&my_addr,sizeof (struct sockaddr))==-1))
    {
        perror("bind");
        exit(1);
    }
    int cnt;
    int i;
    for(i= 0 ;i<10;i++)
    {
        cnt = 0;
        start = clock();
        while(1)
        {
        memset(buf, 0, sizeof(buf));
            recvfrom(listener,buf,sizeof(buf),0,(struct sockaddr *)&peer_addr,&len);
        printf("buf:%s\n", buf);
            ++cnt;
            if(cnt == 10)
                break;
        }
        finish = clock();
        time +=  (double)(finish - start)/CLOCKS_PER_SEC;
    printf("%lf \n",time/10);
    }
    printf("%lf \n",time/10);
    close(listener);
    close(kdpfd);
    return 0;
}

结果：

root@mingji:/home/mingji/share/test# ./server
buf:123
buf:123
buf:123
buf:123
buf:123
buf:123
buf:123
buf:123
buf:123
buf:123
0.000000

上面服务器代码弄到有问题：
服务器：

  #include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<errno.h>
#include<unistd.h>
#include<sys/wait.h>
#include<signal.h>
#include<stdio.h>
#include<fcntl.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#include<time.h>
#define MAXBUF 1024
int main (void)
{
    int listener,kdpfd,nfds,n;
    socklen_t len;
    char buf[100];
    len = sizeof(struct sockaddr_in);
    struct sockaddr_in my_addr,peer_addr;
    clock_t start,finish;
    double time;
    if((listener=socket(PF_INET,SOCK_DGRAM,0))<=-1)
    {
        perror(" socket ");
        exit(1);
    }
    int  opt=SO_REUSEADDR;
    if(setsockopt(listener,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt))==-1)
    {
        perror("setsockopt");
        exit(1);
    }
    bzero(&my_addr,sizeof(my_addr));
    my_addr.sin_family = AF_INET;
    my_addr.sin_port = htons(12345);
    my_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    if((bind(listener,(struct sockaddr *)&my_addr,sizeof (struct sockaddr))==-1))
    {
        perror("bind");
        exit(1);
    }
    int cnt;
    int i;
    for(i= 0 ;i<10;i++)
    {
        cnt = 0;
        start = clock();
        while(1)
        {
        memset(buf, 0, sizeof(buf));
            recvfrom(listener,buf,sizeof(buf),0,(struct sockaddr *)&peer_addr,&len);
        printf("buf:%s\n", buf);
            ++cnt;
            if(cnt == 10)
                break;
        }
        finish = clock();
        time +=  (double)(finish - start)/CLOCKS_PER_SEC;
    printf("%lf \n",time/10);
    }
    printf("%lf \n",time/10);
    close(listener);
    close(kdpfd);
    return 0;
}

结果：

root@mingji:/home/mingji/share/test# ./server
buf:123
buf:123
buf:123
buf:123
buf:123
buf:123
buf:123
buf:123
buf:123
buf:123
0.000000