代碼筆記 | TCP網絡協議編程實現

 
/******* 服務器程序  (server.c) ************/
#include <stdlib.h> 
#include <stdio.h> 
#include <errno.h> 
#include <string.h> 
#include <unistd.h> 
#include <netdb.h> 
#include <sys/socket.h> 
#include <netinet/in.h> 
#include <sys/types.h> 
#include <arpa/inet.h> 
  
int main(int argc, char *argv[]) { 
    int sockfd,new_fd;         
    struct sockaddr_in server_addr;         
    struct sockaddr_in client_addr;         
    int sin_size,portnumber; 
    char hello[]="Hello! Are You Fine?\\n";        
    if(argc!=2)        
    { 
       fprintf(stderr,"Usage:%s portnumber\\a\\n",argv[0]);                 
        exit(1);         
    } 
    if((portnumber=atoi(argv[1]))<0)         
    { 
        fprintf(stderr,"Usage:%s portnumber\\a\\n",argv[0]);                 
        exit(1);         
    } 
    /* 服務器端開始建立socket描述符 */       
    if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)           
    { 
         fprintf(stderr,"Socket error:%s\\n\\a",strerror(errno));                 
         exit(1);         
    } 
    /* 服務器端填充 sockaddr結構  */ 
    zero(&server_addr,sizeof(struct sockaddr_in)); 
  
    server_addr.sin_family=AF_INET; 
    server_addr.sin_addr.s_addr=htonl(INADDR_ANY);         
    server_addr.sin_port=htons(portnumber);         
    /* 捆綁sockfd描述符  */ 
    if(bind(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr))==-1) 
    { 
         fprintf(stderr,"Bind error:%s\\n\\a",strerror(errno));                 
         exit(1);         
    } 
    /* 監聽sockfd描述符  */
    if(listen(sockfd,5)==-1)         
   { 
       fprintf(stderr,"Listen error:%s\\n\\a",strerror(errno));                 
       exit(1);        
   }        
   while(1) 
   { 
        /* 服務器阻塞,直到客戶程序建立連接  */                
        sin_size=sizeof(struct sockaddr_in);                
        if((new_fd=accept(sockfd,(struct sockaddr *)(&client_addr),&sin_size))==-1) 
        { 
            fprintf(stderr,"Accept error:%s\\n\\a",strerror(errno));                         
            exit(1);                 
        } 
          
        fprintf(stderr,"Server get connection from %s\\n", inet_ntoa(client_addr.sin_addr)); 
        if(write(new_fd,hello,strlen(hello))==-1)//if(send(new_fd,hello,strlen(hello),0)==-1)             
        { 
             fprintf(stderr,"Write Error:%s\\n",strerror(errno));                        
             exit(1); 
        } 
        /* 這個通訊已經結束 */                
        close(new_fd); 
        /* 循環下一個     */   
    }   
    close(sockfd);        
    exit(0); 
}
   
/******* 客戶端程序  client.c ************/
#include <stdlib.h> 
#include <stdio.h> 
#include <errno.h> 
#include <string.h> 
#include <unistd.h> 
#include <netdb.h> 
#include <sys/socket.h> 
#include <netinet/in.h>
#include <sys/types.h> 
#include <arpa/inet.h> 
int main(int argc, char *argv[]) 
{ 
    int sockfd; 
    char buffer[1024]; 
    struct sockaddr_in server_addr;         
    struct hostent *host;         
    int portnumber,nbytes; 
    if(argc!=3)         
    { 
        fprintf(stderr,"Usage:%s hostname portnumber\\a\\n",argv[0]);                 
        exit(1);         
    } 
    if((host=gethostbyname(argv[1]))==NULL)         
    { 
        fprintf(stderr,"Gethostname error\\n");                 
        exit(1);         
    } 
    if((portnumber=atoi(argv[2]))<0)        
    { 
            fprintf(stderr,"Usage:%s hostname portnumber\\a\\n",argv[0]);                 
        exit(1);         
    } 
    /* 客戶程序開始建立 sockfd描述符  */
    if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)        
    { 
           fprintf(stderr,"Socket Error:%s\\a\\n",strerror(errno)); 
           exit(1);        
    } 
    /* 客戶程序填充服務端的資料*/        
    bzero(&server_addr,sizeof(server_addr));         
    server_addr.sin_family=AF_INET; 
    server_addr.sin_port=htons(portnumber); 
    server_addr.sin_addr=*((struct in_addr *)host->h_addr);         
    /* 客戶程序發起連接請求*/ 
    if(connect(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr))==-1)        
    { 
         fprintf(stderr,"Connect Error:%s\\a\\n",strerror(errno));                 
         exit(1);         
    } 
    /* 連接成功了*/
    if((nbytes=read(sockfd,buffer,1024))==-1)  //if((nbytes=recv(sockfd,buffer,1024))==-1)       
    { 
         fprintf(stderr,"Read Error:%s\\n",strerror(errno));                
         exit(1);         
    } 
    buffer[nbytes]='\\0'; 
    printf("I have received:%s\\n",buffer);         
    /* 結束通訊     */        
    close(sockfd);         
    exit(0); 
}