. Net 5 fluentftp connection FTP failure problem: this operation is only allowed using a successfully authenticated context

background ： Used in the test environment FluentFTP Connect FTP That's all right. , There is no connection to the customer

Problem analysis ：

1. Look at the error message , It's certification , Checked FTP The account and password are ok

2. Check the customer FTP Server, yes Sery-U Built , It is possible to connect with the client

3. That's the procedural problem , The suspicion is FluentFTP problem , But view FluentFTP, Yes, it supports connection Serv-U Of ; Because I don't want to change too many things in the program , So I started to analyze FluentFTP Use of

4. Check the initialization FTPClient Method , After trying to replace , Invalid ; It is found that the connection is used AutoConnect, It feels like this is bad Auto Yes

to glance at AutoConnect effect ：

  This makes up a little knowledge ,FTPS Is in FTP On the basis of TLS and SSL The certification , But and based on SSH Of FTP It's different （ namely SFTP）. that AutoConnect It should be automatic recognition FTP still FTPS, Then connect . Here it should be considered FTPS, And then connect , At the same time, our connection information is missing for FTPS Credentials for connection authentication , Lead to failure ;

solve ： take AutoConnect Change it to Connect Just fine ;

Yan Shen ：

Decompile and check AutoConnect Source code ：

He is getting multiple FtpProfile, And take the first one to connect ;

see AutoDetect In the method , There is obviously a lot about SSL The operation of , But I'm not sure which operation caused this error

summary ： about AutoConnect and Connect Still use it cautiously