udp使用select

服务器：

#include <stdio.h>

#include <sys/select.h>

#include <sys/time.h>

#include <sys/types.h>

#include <unistd.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include<errno.h>

#define MAX_MSG_SIZE 1024

int main()

{ 

    int ser_sockfd,cli_sockfd; /*sock_fd：监听socket；client_fd：数据传输socket */ 

    struct sockaddr_in ser_addr; /* 本机地址信息 */ 

    struct sockaddr_in cli_addr; /* 客户端地址信息 */ 

    char msg[MAX_MSG_SIZE];/* 缓冲区*/

memset(&cli_addr, 0,sizeof(cli_addr));

socklen_t len = sizeof(cli_addr);

    ser_sockfd=socket(AF_INET,SOCK_DGRAM,0);/*创建连接的SOCKET */

    if(ser_sockfd<0)

    {/*创建失败 */

        fprintf(stderr,"socker Error:%s\n",strerror(errno));

       return 0;

    } 

    /* 初始化服务器地址*/

    int addrlen=sizeof(struct sockaddr_in);

    bzero(&ser_addr,addrlen);

    ser_addr.sin_family=AF_INET;

    ser_addr.sin_addr.s_addr=inet_addr("127.0.0.1");   

    ser_addr.sin_port=htons(8888);

    if(bind(ser_sockfd,(struct sockaddr*)&ser_addr,sizeof(struct sockaddr_in))<0)

    { /*绑定失败 */

        fprintf(stderr,"Bind Error:%s\n",(char *)strerror(errno));

        return 0;

    } 

printf("enter while\n");

fd_set readfds;

int selectresult;

    while(1)

    {/* 等待接收客户连接请求*/

        FD_ZERO(&readfds);

        FD_SET(ser_sockfd, &readfds);

        selectresult = select(FD_SETSIZE, &readfds, NULL, NULL, NULL);

        if (selectresult <= 0){

            printf("[%S] select error\n",__FUNCTION__);

            usleep(50 * 1000);

            continue;

        }

//int length = recvfrom(ser_sockfd,msg,MAX_MSG_SIZE,0,(struct sockaddr*)&cli_addr, sizeof(struct sockaddr_in)); //错误sizeof(struct sockaddr_in)下发要是地址

         int length = recvfrom(ser_sockfd,msg,MAX_MSG_SIZE,0,(struct sockaddr*)&cli_addr, &len); /* 接受数据*/

           // printf("received a connection from ip=%s,port=%d\n", inet_ntoa(cli_addr.sin_addr.s_addr),ntohs(cli_addr.sin_port));

 printf("length=%d\n",length);

// printf("recvfrom Error:%d\n",errno);

if(length > 0){

            printf("%s\n",msg);/*在屏幕上打印出来 */ 

            strcpy(msg,"hi,I am server!");

            sendto(ser_sockfd,msg,strlen(msg),0,(struct sockaddr*)&cli_addr, sizeof(cli_addr)); /*发送的数据*/

}

    }

    close(ser_sockfd);

}

客户端：

#include <stdio.h>

#include <sys/select.h>

#include <sys/time.h>

#include <sys/types.h>

#include <unistd.h>

#include <sys/socket.h>

#include <netinet/in.h>

int main(int argc, char* argv[])  

{  

int addrlen=sizeof(struct sockaddr_in);

    int sclient = socket(AF_INET, SOCK_DGRAM, 0);  

int i = 10;

    if(sclient < 0)  

    {  

        printf("invalid socket !");  

        return 0;  

    }  

  

struct sockaddr_in serAddr,cAddr;  

    serAddr.sin_family = AF_INET;  

    serAddr.sin_port = htons(8888);  

    serAddr.sin_addr.s_addr = inet_addr("127.0.0.1");   

  memset(&cAddr, 0,sizeof(cAddr));

socklen_t len = sizeof(cAddr);

    char * sendData = " hello tcp server i am  client\n";  

while(i > 0){

int length = sendto(sclient, sendData, strlen(sendData),0, (struct sockaddr*)&serAddr, sizeof(serAddr));  

printf("sendto data length=%d\r\n",length);  

char recData[255];  

int ret = recvfrom(sclient, recData, 255,0, (struct sockaddr*)&cAddr, &len);  

if(ret > 0)  

{  

  recData[ret] = 0x00;  

  printf("recData=%s\r\n",recData);  

}  

sleep(1);

i--;

}

    close(sclient);  

    return 0;  

}