Linux UDP socket编程(UDP通讯模型)：

UDPClient + UDPService。

Linux下大多数网络程序都是基于TCP的，很少基于UDP，简单的通讯模型如下，开发时候备用！

udpService:

[cpp]

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#define SERVER_PORT 2222

#define MAX_SIZE 1024

void UDP_answer(int sockfd)

{

struct sockaddr_in addr;

int i,n;

unsigned int addrlen;

char msg[MAX_SIZE];

while(1)

{

n=recvfrom(sockfd,msg,MAX_SIZE,0,(struct sockaddr *)&addr,&addrlen);

msg[n]=0;

fprintf(stdout,"i have received %s",msg);

n=strlen(msg);

for(i=0;i

msg[i]=toupper(msg[i]);

sendto(sockfd,msg,n,0,(struct sockaddr *)&addr,addrlen);

}

}

int main(void)

{

int sockfd;

struct sockaddr_in addr;

sockfd=socket(AF_INET,SOCK_DGRAM,0);

bzero(&addr,sizeof(struct sockaddr_in));

addr.sin_family=AF_INET;

addr.sin_addr.s_addr=htonl(INADDR_ANY);

addr.sin_port=htons(SERVER_PORT);

if(bind(sockfd,(struct sockaddr *)&addr,sizeof(struct sockaddr_in))<0)

{

perror("bind");

exit(1);

}

UDP_answer(sockfd);

close(sockfd);

return 0;

}

[/cpp]

udpClient:

[cpp]

#include

#include

#include

#include

#include

#include

#include

#include

#include

#define MAX_SIZE 1024

void UDP_ask(int sockfd,const struct sockaddr_in *addr,int len)

{

char buf[MAX_SIZE];

int n;

while(1)

{

fgets(buf,MAX_SIZE,stdin);//input from keyboard to service

sendto(sockfd,buf,strlen(buf),0,(struct sockaddr *)addr,len);

printf("i have sent to server %s",buf);

printf("Waiting answer from server\n");

bzero(buf,MAX_SIZE);

n=recvfrom(sockfd,buf,MAX_SIZE,0,NULL,NULL);

buf[n]=0;

printf("i have received from server");

fputs(buf,stdout);

printf("\n");

}

}

int main(int argc,char **argv)

{

int sockfd,port;

struct sockaddr_in addr;

if(argc!=3){

fprintf(stderr,"Usage:%s sercer_ip server_port\n",argv[0]);

exit(1);

}

if((port=atoi(argv[2]))<0){

fprintf(stderr,"Usage:%s server_ip server_port\n",argv[0]);

exit(1);

}

sockfd=socket(AF_INET,SOCK_DGRAM,0);

bzero(&addr,sizeof(struct sockaddr_in));

addr.sin_family=AF_INET;

addr.sin_port=htons(port);

if(inet_aton(argv[1],&addr.sin_addr)<0){

fprintf(stderr,"Ip error:%s\n",strerror(errno));

exit(1);

}

UDP_ask(sockfd,&addr,sizeof(struct sockaddr_in));

close(sockfd);

return 0;

}

[/cpp]

运行结果如下：

服务器在后台运行：./udpservice &

回显来自客服端的消息:略(ps可以查看后台进程PID)

客服端：

[cpp]

[root@localhost lab]# ./udpclient 127.0.0.1 2222

cplusplus

i have sent to server cplusplus

Waiting answer from server

i have received from serverCPLUSPLUS

hellowolrld

i have sent to server hellowolrld

Waiting answer from server

i have received from serverHELLOWOLRLD

[/cpp]