Linux C socket通訊端UDP通訊執行個體

//目的，實現遠程擷取伺服器uptime輸出

 //伺服器

#include<stdio.h>#include<stdlib.h>#include<sys/socket.h>#include<arpa/inet.h>#include<string.h>#include<errno.h>#include<unistd.h>#define BUFSIZE 1024int main(void){        struct sockaddr_in local_addr,remote_addr;        int sockfd;        int server_ip,nrecv;        int alen;        FILE *fp;        char buffer[BUFSIZE];        memset(&local_addr,0,sizeof(local_addr));        local_addr.sin_family=AF_INET;        local_addr.sin_port=htons(5666);        inet_pton(AF_INET,"127.0.0.1",(void*)&server_ip);        local_addr.sin_addr.s_addr=server_ip;        sockfd=socket(AF_INET,SOCK_DGRAM,0);        if(bind(sockfd,(struct sockaddr*)&local_addr,sizeof(struct sockaddr))<0){                fprintf(stderr,"error:bind() error!\n");                exit(-1);        }        printf("====================Begin to service====================\n");        while(1){                if((nrecv=recvfrom(sockfd,buffer,BUFSIZE,0,(struct sockaddr*)&remote_addr,&alen))<0){                        fprintf(stderr,"error:%s\n",strerror(errno));                        exit(1);                }else{                        if((fp=popen("/usr/bin/uptime","r"))==NULL){                                fprintf(stderr,"error:%s\n",strerror(errno));                                exit(1);                        }                        if(fgets(buffer,BUFSIZE,fp)!=NULL)                                sendto(sockfd,buffer,strlen(buffer),0,(struct sockaddr*)&remote_addr,alen);                }        }        exit(0);}

//用戶端

#include<stdio.h>#include<stdlib.h>#include<sys/socket.h>#include<arpa/inet.h>#include<syslog.h>#include<unistd.h>#include<errno.h>#include<string.h>#define BUFSIZE 1024int main(void){        int sockfd;        struct sockaddr_in server_addr;        char buffer[BUFSIZE];        int server_ip;        int nrecv;        int alen;        memset(&server_addr,0,sizeof(server_addr));        server_addr.sin_family=AF_INET;        server_addr.sin_port=htons(5666);        inet_pton(AF_INET,"127.0.0.1",(void*)&server_ip);        server_addr.sin_addr.s_addr=server_ip;        sockfd=socket(AF_INET,SOCK_DGRAM,0);        if(sockfd<0){                syslog(LOG_ERR,"ruptime_udp:socket() failed!\n");                exit(1);        }        memset(buffer,0,BUFSIZE);        buffer[0]=0;        alen=sizeof(struct sockaddr);        if(sendto(sockfd,buffer,1,0,(struct sockaddr*)&server_addr,sizeof(struct sockaddr))<0){                syslog(LOG_ERR,"ruptime_udp error:%s\n",strerror(errno));                exit(1);        }        if((nrecv=recvfrom(sockfd,buffer,BUFSIZE,0,(struct sockaddr*)&server_addr,&alen))>=0)                write(STDOUT_FILENO,buffer,nrecv);        exit(0);}

//運行結果

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