未定義的引用_red

Question

我在編寫使用cygwin編寫代碼時編寫了一個簡單的客戶端程序「套接字編程」我得到了這個錯誤「undefined reference to'_red' 下面的代碼我一直在編譯這個語句gcc client .C 我真的不明白爲什麼我收到這個錯誤。我真的可以使用一些幫助。代碼如下。

#include <stdio.h> 
#include <sys/types.h> 
#include <sys/socket.h> 
#include <netdb.h> 
#include <stdlib.h> 
#include <strings.h> 
#include <netinet/in.h> 

#define SERVER_TCP_PORT 2000 
#define BUFLEN 256 

int main(int argc,char **argv) 
{ 
    int n,bytes_to_read; 
    int sd,port; 
    struct hostent *hp; 
    struct sockaddr_in server; 
    char *host,*bp,rbuf[BUFLEN],sbuf[BUFLEN]; 
    switch(argc) { 
     case 2: 
      host = argv[1]; 
      port = atoi(argv[2]); 
      break; 
     default: 
      fprintf(stderr,"Usage: %s host[port] \n",argv[0]); 
      exit(1); 
    } 
    /*Create a streamm socket*/ 
    if ((sd=socket(AF_INET,SOCK_STREAM,0))==-1){ 
     fprintf(stderr,"Can't create a socket\n"); 
     exit(1); 
    } 
    bzero ((char *)&server,sizeof(struct sockaddr_in)); 
    server.sin_family = AF_INET; 
    server.sin_port = htons(port); 
    if((hp = gethostbyname(host))==NULL){ 
     fprintf (stderr,"Can't get server's address\n"); 
     exit(1); 
    } 
    //bcopy(hp->h_addr,(char *)&server.sin_addr,hp->h_length); 
    /*connecting to the server*/ 
    if (connect (sd,(struct sockaddr *)&server,sizeof(server))==-1){ 
     fprintf(stderr,"Can't connect \n"); 
     exit(1); 
    } 
    printf("Connected:server's address is %s\n",hp->h_name); 
    printf("Transmit: \n"); 
    gets(sbuf);     /*get user's text*/ 
    write (sd,sbuf,BUFLEN);  /*send it out*/ 
    printf("Receive: \n"); 
    bp = rbuf; 
    bytes_to_read = BUFLEN; 
    while ((n=red(sd,bp,bytes_to_read))>0){ 
     bp+=n; 
     bytes_to_read -=n; 
    } 
    printf("%s\n",rbuf); 
    close(sd); 
    return(0); 
} 

Answer 1

上線

while ((n=red(sd,bp,bytes_to_read))>0){ 

它有紅，你可能平均讀數爲