如何从 FTP 服务器读取多行响应？

Question

我正在用 C 编写 FTP 客户端程序。我正在使用阻塞套接字。我已将 recv () 放入 while 循环中，当最后两个接收到的字符为 \r\n 时我将其中断。我可以在某些服务器上运行它但它不会在某些服务器上读取整个消息，例如 ftp.secyt.gov.ar.

我认为问题是因为来自服务器的消息同时包含 \r \n 个字符。

遇到这种情况应该怎么处理？

将用户名和密码发送到服务器 ftp.secyt.gov.ar 后，我想打印从服务器收到的消息。

password = getpass("Password: ");
sprintf(pass, "PASS %s\r\n",password);

send(sockfd, pass, strlen(pass), 0);

while((no_of_bytes = recv(sockfd, message_from_server, MAXSZ, 0)) > 0)
{
    message_from_server[no_of_bytes] = '[=11=]';
    printf("%s\n", message_from_server);

    if (message_from_server[no_of_bytes-2] == '\r' &&
        message_from_server[no_of_bytes-1] == '\n')
        break;
}

服务器发送此消息：

230-=====================================================================

    BIENVENIDOS AL SERVIDOR FTP DE LA MINCyT   
             ----------------------------------------

Usuario anonymous, desde la maquina ::ffff:116.203.73.60, gracias por
utilizar el FTP del Ministerio de Ciencia, Tecnologia e
Innovacion Productiva.

Para sugerencias, consultas o informacin adicional nuestros correos 
electrnicos son:
                     webmaster@mincyt.gov.ar

=========================================================================
230 User anonymous logged in.

但它只是打印:

230-=====================================================================

Answer 1

您的代码从服务器读取一行（以 \r\n 结尾的字符串）。

但是根据 FTP 规范，FTP 响应可以是多行的。

查看 RFC 959, section 4.2 FTP Replies:

Thus the format for multi-line replies is that the first line will begin with the exact required reply code, followed immediately by a Hyphen, "-" (also known as Minus), followed by text. The last line will begin with the same code, followed immediately by Space , optionally some text, and the Telnet end-of-line code.

For example:
 123-First line  
 Second line  
   234 A line beginning with numbers  
 123 The last line
The user-process then simply needs to search for the second occurrence of the same reply code, followed by (Space), at the beginning of a line, and ignore all intermediary lines. If an intermediary line begins with a 3-digit number, the Server must pad the front to avoid confusion.

另见 How to know the end of FTP Welcome message。

如何从 FTP 服务器读取多行响应？

How to read multiline response from FTP server?

ftp

ftp-client

unix-socket