[問題] client和server問題

[ful6up (今天不回家)]

不太清楚裡面是怎樣運作的
以下是程式碼

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include<sys/socket>
//#include <winsock2.h>
#include <resolv.h>
//#include<windows.h>
#define PORT_TIME       13              /* "time" (not available on RedHat) */
#define PORT_FTP        21              /* FTP connection port */
#define SERVER_ADDR     "127.0.0.1"     /* localhost */
#define MAXBUF          1024

int main()
{   int sockfd;
    struct sockaddr_in dest;
    char buffer[MAXBUF];

    /*---Open socket for streaming---*/
    if ( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0 )
    {
        perror("Socket");
        exit(errno);
    }

    /*---Initialize server address/port struct---*/
    bzero(&dest, sizeof(dest));//copy zero to the string
    dest.sin_family = AF_INET;//AF-INET ===>internet protocols
    dest.sin_port = htons(PORT_FTP);//set port
    if ( inet_aton(SERVER_ADDR, &dest.sin_addr.s_addr) == 0 )//inet_aton()
convert ip address to integer
    {
        perror(SERVER_ADDR);
        exit(errno);
    }

    /*---Connect to server---*/
    if ( connect(sockfd, (struct sockaddr*)&dest, sizeof(dest)) != 0
)//connect socket
    {
        perror("Connect ");
        exit(errno);
    }

    /*---Get "Hello?"---*/
    bzero(buffer, MAXBUF);
    recv(sockfd, buffer, sizeof(buffer), 0);
    printf("%s", buffer);

    /*---Clean up---*/
    close(sockfd);
    return 0;
}


執行結果:
connection refused

不是去連結本機嗎?
並起連結port:21的地方
為何還會有無法連結的情況??
請版上神人指導一下
感激

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◆ From: 140.116.16.190
→ james732:你的電腦有執行FTP server程式嗎？
→ ful6up:有~但是還是連不進去...
→ MiLu307:check the firewall setting?
推 antontw:telnet 127.0.0.1 21 先？
→ ful6up:感謝~可以使用了!!