网络通信（udp协议）

用udp协议实现echo服务器（即服务器把收到的内容发送回去）

服务器：socket->bind->(recvfrom->sendto)循环

客户端：socket->connect->(recvfrom->sendto)循环

Server.c

#include<stdio.h>

#include<stdlib.h>

#include<string.h>

#include<unistd.h>

#include<sys/types.h>

#include<sys/socket.h>

#include<netinet/in.h>

#include<arpa/inet.h>

#define MAXLINE 50

typedef struct sockaddr SA;

int main(int argc,char **argv)

{

int sockfd;

socklen_t peerlen;

struct sockaddr_in myaddr,peeraddr;

char buf[MAXLINE];

if((sockfd=socket(PF_INET,SOCK_DGRAM,0))<0)

{

printf("fail to socket\n");

exit(-1);

}

bzero(&myaddr,sizeof(myaddr));

myaddr.sin_family=PF_INET;

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

myaddr.sin_port=htons(8888);

if(bind(sockfd,(SA *)&myaddr,sizeof(myaddr))<0)

{

printf("fail to bind\n");

exit(-1);

}

while(1)

{

peerlen=sizeof(peeraddr);

recvfrom(sockfd,buf,sizeof(buf),0,(SA *)&peeraddr,&peerlen);

printf("connection from %s,port %d\n",inet_ntoa(peeraddr.sin_addr),ntohs(peeraddr.sin_port));

sendto(sockfd,buf,sizeof(buf),0,(SA *)&peeraddr,sizeof(peeraddr));

}

return 0;

}

Client.c

#include<stdio.h>

#include<stdlib.h>

#include<string.h>

#include<unistd.h>

#include<sys/types.h>

#include<sys/socket.h>

#include<netinet/in.h>

#include<arpa/inet.h>

#define MAXLINE 50

typedef struct sockaddr SA;

int main()

{

int sockfd,nbyte;

struct sockaddr_in servaddr;

char buf[MAXLINE]="hello Server";

if((sockfd=socket(PF_INET,SOCK_DGRAM,0))<0)

{

printf("fail to socket\n");

exit(-1);

}

bzero(&servaddr,sizeof(servaddr));

servaddr.sin_family =PF_INET;

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

servaddr.sin_port=htons(8888);

if(connect(sockfd,(SA *)&servaddr,sizeof(servaddr))<0)

{

printf("fail to connect\n");

exit(-1);

}

sendto(sockfd,buf,sizeof(buf),0,(SA *)&servaddr,sizeof(servaddr));

bzero(buf,sizeof(buf));

recvfrom(sockfd,buf,MAXLINE,0,NULL,NULL);

printf("recv from server:%s\n",buf);

return 0;

}