我写FTPS服务器,我在AUTH TLS命令后遇到ssl连接问题.
简单的例子：

try
{
    int ServerPort = 21;
    ServerSocket FtpExServer = new ServerSocket(ServerPort);
    while(true)
    {
        Socket S = FtpExServer.accept();
        InputStreamReader ISR = new InputStreamReader(S.getInputStream());
        OutputStreamWriter OSW = new OutputStreamWriter(S.getOutputStream());
        BufferedReader ClientSocketReader = new BufferedReader(ISR);
        PrintWriter ClientSocketWriter = new PrintWriter(OSW, true);

        ClientSocketWriter.println("220 Welcome to FTP server.");
        print(ClientSocketReader.readLine());
        ClientSocketWriter.println("234 AUTH TLS successful");

        char[] passphrase = "pass".toCharArray();
        char[] cpassphrase = "cpass".toCharArray();
        KeyStore keystore = KeyStore.getInstance("JKS");
        keystore.load(new FileInputStream("keystore.jks"), passphrase);
        KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509");
        kmf.init(keystore, cpassphrase);
        SSLContext context = SSLContext.getInstance("TLS");
        KeyManager[] keyManagers = kmf.getKeyManagers();
        context.init(keyManagers, null, null);
        SSLServerSocketFactory ssf = context.getServerSocketFactory();

        SSLServerSocket ss = (SSLServerSocket) ssf.createServerSocket(990);
                ss.setSoTimeout(2000);          
                SSLSocket s = (SSLSocket)ss.accept();

        ISR = new InputStreamReader(s.getInputStream());
        OSW = new OutputStreamWriter(s.getOutputStream());
        ClientSocketReader = new BufferedReader(ISR);
        ClientSocketWriter = new PrintWriter(OSW, true);

        ClientSocketWriter.println("234 AUTH TLS successful");
        print(ClientSocketReader.readLine());
        ClientSocketWriter.println("331 Password required for smie");
        print(ClientSocketReader.readLine());
        ClientSocketWriter.println("230 User smie logged in");
        print(ClientSocketReader.readLine());
        ClientSocketWriter.println("215 UNIX Type: L8");
        print(ClientSocketReader.readLine());
        ClientSocketWriter.println("550 Command not suported.");
    }
}
catch(Exception e)
{
    print(e);
}

说明：FTP客户端(例如MoveITFreely)连接到端口21上的服务器.发送命令“AUTH TLS”后,服务器发送“234 AUTH TLS成功”.现在客户端必须连接到端口990(？)上的服务器,但客户端不连接并获得超时异常.

我做错了什么？

解决方法:

有两种方法可以将SSL添加到FTP.

第一种方法称为隐式SSL.这意味着服务器正在侦听端口990,当客户端连接到它时,首先执行SSL / TLS协商,然后将建立的连接用作通信的命令通道(对于数据通道,SSL握手也在类似的方式).

第二种方法是您尝试使用的方法.它被称为显式SSL.客户端在端口21上连接,发送AUTH TLS并在现有连接上启动SSL协商.根据您的需要,可以保护数据通道或不保护数据通道(使用PROT命令指定).

你混合了方法.我建议你在走得更远之前阅读detailed explanation in Wikipedia.然后阅读RFC for explicit TLS.

更新：您还需要SSLClientSocket,而不是SSLServerSocket.