数据套接字

数据套接字是UDP协议，是一无连接，不可靠的数据报协议。

不允许listen和accept函数

数据报套接字上发送和接受数据的正常方法是sendto和recvfrom

int recvfrom(int socket, void *buffer,size_t size, int flags, struct sockaddr *from, size_t *addrlen);

int sendto(int socket, void *buffer, szie_t, int flags,strcut sockaddr* to, size_t addrlen);

socket套接字描述符，

buffer指向读写缓冲区的指针；

szie读取的字节数

服务端#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>
int main()
{
int sockfd,nbytes;
struct sockaddr_in addr;
socklen_t size;
char message[1024];
sockfd=socket(AF_INET,SOCK_DGRAM,0);
if(sockfd<0)
{
printf("Socket created failed.\n");
return -1;
}
bzero(&addr,sizeof(addr));
addr.sin_family=AF_INET;
addr.sin_port=htons(7766);
addr.sin_addr.s_addr=htonl(INADDR_ANY);
if(bind(sockfd, (struct sockaddr *)&addr, sizeof(addr))<0)
{
printf("bind failed.\n");
return -1;
}
while(1)
{
size=sizeof(addr);
nbytes=recvfrom(sockfd,message,1024,0,(struct sockaddr *)&addr,&size);
if(nbytes<0)
{
printf("recvfrom(server) failed.\n");
return -1;
}
printf("Server recv Client %d bytes is %s \n",strlen(message)-1,message);
nbytes = sendto(sockfd,message,nbytes, 0, (struct sockaddr*)&addr, size);
if(nbytes<0)
{
printf("send to failed\n");
return -1;
}

}
}
客户端
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

int main()
{
int sockfd,n;
char recvbuff[512],sndbuff[512];
struct sockaddr_in servaddr;
sockfd=socket(AF_INET,SOCK_DGRAM,0);
if(sockfd<0)
{
printf("Socket created failed.\n");
return -1;
}

servaddr.sin_family=AF_INET;
servaddr.sin_port=htons(7766);
servaddr.sin_addr.s_addr=htonl(INADDR_ANY);
while(fgets(sndbuff,512,stdin)!=NULL)
{
if(sendto(sockfd,sndbuff,sizeof(sndbuff),0,(struct sockaddr*)&servaddr,sizeof(servaddr))<0)
{
printf("(client)sending error.\n");
return -1;
}
if((n = recvfrom(sockfd, recvbuff,512, 0 , NULL, NULL))<0)
{
printf("client recv error\n");
return -1;
}

printf("client received is : %s",recvbuff);
}
close(sockfd);
return 0;
}
运行
先运行服务端，后客户端。

在客户端输入发送给服务端，服务端接受到并打印，原样发送客户端。