如何在嵌入式设备上设置FTP客户端连接？

Question

我在一个mbed项目的FTP脚本上工作。我使用B-L475E-IOT01A开发板，尝试将文件发送到FTP-Server。因此，我不能用这个库https://os.mbed.com/users/dkato/code/ftp-client/#e069c405c934建立与服务器的连接。不幸的是，客户端并没有像它应该工作的那样工作。我试着像这样建立连接：

bool FTPClient::open(const char* ip_addr, int port, const char* user, const char* pass)
{
    SocketAddress ftpAddress(ip_addr, port);

    //Connect to SocketAddress while using FTP Clients Network interface
    FTPClientControlSock.open(p_network);
    if (FTPClientControlSock.connect(ftpAddress) < 0) {
        printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
        return false;
    }

    //recieve ftp server message
    if (FTPClientControlSock.recv(p_ftp_buf, FTP_BUF_SIZE) <= 0) {
        printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
        return false;
    }

    //prove ftp server message equals ftp server information messages (starting with not logged in code 220)
    if (strncmp(p_ftp_buf, "220", 3) != 0) {
        printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
        return false;
    }

    //store user info in ftp communication and send it
    sprintf(p_ftp_buf, "USER %s\r\n", user);
    printf("%s", p_ftp_buf);
    FTPClientControlSock.send(p_ftp_buf, strlen(p_ftp_buf));

    //recieve ftp server info and print it
    if (FTPClientControlSock.recv(p_ftp_buf, FTP_BUF_SIZE) <= 0) {
        printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
        return false;
    }
    printf("%s", p_ftp_buf);

    //prove ftp server message equals ftp server information messages (begin with code 331)
    if (strncmp(p_ftp_buf, "331", 3) != 0) {
        printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
        return false;
    }

    //store password in string and send it to server
    sprintf(p_ftp_buf, "PASS %s\r\n", pass);
    printf("%s", p_ftp_buf);
    FTPClientControlSock.send(p_ftp_buf, strlen(p_ftp_buf));

    //recieve ftp server info and print it
    if (FTPClientControlSock.recv(p_ftp_buf, FTP_BUF_SIZE) <= 0) {
        printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
        return false;
    }

    //check login was successful
    if (strncmp(p_ftp_buf, "230", 3) != 0) {
        printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
        return false;
    }

    printf("%s", p_ftp_buf);
    return true;
}

在终端上，之后我在控制台中得到如下输出：

220---------- Welcome to Pure-FTPd [privsep] [TLS] ----------
220-You are user number 4 of 500 allowed.
220-Local time is now 02:42. Server port: 21.
220-This is a private system - No anonymous login
220 You will be disconnected after 15 minutes of inactivity.
USER user
PASS pass
331 User user OK. Password required
is now 02:42. Server port: 21.
220-This is a private system - No anonymous login
220 You will be disconnected after 15 minutes of inactivity.
ERROR: ./ftp-client/FTPClient.cpp(96) //this is the line where the code 230 gets checked

我真的不知道我的错误在哪里。我希望能成功登录，并与ftp服务器进行清晰的通信。你能帮我吗？

Answer 1

Julien，所有来自服务器的响应都遵循一个模式..您需要等待来自服务器的\r\n序列。您需要过滤TELNET协议转义序列(以字节0xff或0xfe开头，我不记得了)，代码必须始终位于行的开头。同样，带有-而不是空格的数字表明消息更大，您应该期待另一行(每条消息的最后一行后面跟着一个空格)

这对于保持您与服务器的同步是必不可少的……否则，您将开始收到与您认为的命令不同的响应。

从输出中不清楚您试图做什么，因为您唯一显示的是到服务器的登录部分。

您的命令行还必须(根据协议，这是强制性的)以序列\r\n (按该顺序)结束，否则您不能这样做，或者您可以到达不理解您的服务器。

有关ftp协议如何工作的详细信息，请查看RFC-959 - File Transfer Protocol。传输通常在一个新的、不同的TCP连接中处理，因此您通常必须管理控制连接以及与其并行运行的一系列数据传输。

Answer 2

好了，我终于建立了连接。同步服务器和客户端是正确的。此外，我需要时不时地释放缓冲区，现在输出不那么混乱了。下面是我的代码：

bool FTPClient::open(const char *ip_addr, int port, const char *user,
                 const char *pass) {


// Convert into SocketAddress
  SocketAddress ftpAddress(ip_addr, port);

  // Close FTP connection if open
  if (_ctr_open) {
    FTPClientControlSock.close();
  }

  // Connect to SocketAddress while using FTP Clients Network interface
  FTPClientControlSock.open(p_network);
  if (FTPClientControlSock.connect(ftpAddress) < 0) {
    printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
    return false;
  }

  // set connection to true
  _ctr_open = true;

  // recieve ftp server messages and print if correct
  if (FTPClientControlSock.recv(p_ftp_buf, FTP_BUF_SIZE) <= 0) {
    printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
    return false;
  }
  if (strncmp(p_ftp_buf, "220", 3) != 0) {
    printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
    return false;
  } else {
    printf("%s", p_ftp_buf);
    _login = false;
  }
  wait_us(2000000);
  memset(p_ftp_buf, 0, strlen(p_ftp_buf));

  if (FTPClientControlSock.recv(p_ftp_buf, FTP_BUF_SIZE) <= 0) {
    printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
    return false;
  }
  if (strncmp(p_ftp_buf, "220", 3) != 0) {
    printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
    return false;
  } else {
    printf("%s", p_ftp_buf);
    _login = false;
  }
  wait_us(2000000);
  memset(p_ftp_buf, 0, strlen(p_ftp_buf));

  // store user info in ftp communication print and send it
  sprintf(p_ftp_buf, "USER %s\r\n", user);
  FTPClientControlSock.send(p_ftp_buf, strlen(p_ftp_buf));

  // recieve ftp server message and print if correct
  if (FTPClientControlSock.recv(p_ftp_buf, FTP_BUF_SIZE) <= 0) {
    printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
    return false;
  }
  if (strncmp(p_ftp_buf, "331", 3) != 0) {
    printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
    return false;
  } else {
    printf("%s", p_ftp_buf);
    _login = false;
  }
  wait_us(2000000);
  memset(p_ftp_buf, 0, strlen(p_ftp_buf));

  // store password in string and send it to server
  sprintf(p_ftp_buf, "PASS %s\r\n", pass);
  FTPClientControlSock.send(p_ftp_buf, strlen(p_ftp_buf));
  wait_us(2000000);

  // recieve ftp server info and print it
  if (FTPClientControlSock.recv(p_ftp_buf, FTP_BUF_SIZE) <= 0) {
    printf("LINE: %d\r\n", __LINE__);
    printf("%s", p_ftp_buf);
    printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
    return false;
  } else {
    wait_us(3000000);
    printf("%s", p_ftp_buf);
  }
  if (FTPClientControlSock.recv(p_ftp_buf, FTP_BUF_SIZE) <= 0) {
    printf("LINE: %d\r\n", __LINE__);
    printf("%s", p_ftp_buf);
    printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
    return false;
  } else {
    wait_us(3000000);
    printf("%s", p_ftp_buf);
  }

  // check login was successful
  if (strncmp(p_ftp_buf, "230", 3) != 0) {
    printf("ERROR: %s(%d)\r\n", __FILE__, __LINE__);
    return false;
  }

  memset(p_ftp_buf, 0, strlen(p_ftp_buf));
  _login = true;
  return true;
}

我得到了输出：

220---------- Welcome to Pure-FTPd [privsep] [TLS] ----------
220-You are user number 4 of 500 allowed.
220-Local time is now 03:25. Server port: 21.
220-This is a private system - No anonymous login
220 You will be disconnected after 15 minutes of inactivity.
331 User user OK. Password required
230-Your bandwidth usage is restricted
230-OK. Current restricted directory is /
230 1941 Kbytes used (0%) - authorized: 2048000 Kb
FTP Connection successful

谢谢你对我的照顾。