how can i solve this issue? I read that is a bug in rclone? Is that true?
rclone version
rclone v1.63.0
os/version: ubuntu 22.04 (64 bit)
os/kernel: 5.15.0-76-generic (x86_64)
os/type: linux
os/arch: amd64
go/version: go1.20.5
go/linking: static
go/tags: none
Problem:
2023/07/14 23:58:24 ERROR : MYFILE******: vfs cache: failed to upload try #6, will retry in 5m0s: vfs cache: failed to transfer file from cache to remote: update stor: 1 error occurred:
425 Unable to build data connection: TLS session of data connection not resumed.
Reproduce?
Setup FileZilla Server with v1.7.2, mount this FTP with the given command. Try to transfer diffrent files.
**Describe the bug**
I am using Explicit FTPS to connect to a FileZilla Server …(1.5.1). When I'm downloading a file a certain amount of times the server gives me an error and the control connection gets closed.
**To Reproduce**
```
c, err := ftp.Dial("127.0.0.1:21", ftp.DialWithExplicitTLS(&tls.Config{
ClientSessionCache: tls.NewLRUClientSessionCache(0),
InsecureSkipVerify: true,
ServerName: "test",
}))
if err != nil {
log.Fatal(err)
}
err = c.Login("user", "pass")
if err != nil {
log.Fatal(err)
}
for i := 0; i < 200; i++ {
fmt.Println("Round " + fmt.Sprint(i))
r, err := c.Retr("/testfile.txt")
if err != nil {
panic(err)
}
buf, _ := ioutil.ReadAll(r)
println(string(buf))
r.Close()
}
```
**Expected behavior**
I would expect that no matter how many files I download, the control connection will not be closed. When I am connecting without TLS this is no problem. Also using WinSCP to connect to the Server or a FileZilla Client works fine.
**FTP server**
- Name and version: FileZilla 1.5.1
**Debug output**
The go FTP Client gives me the following error:
```
panic: write tcp 127.0.0.1:61864->127.0.0.1:21: wsasend: An existing connection was forcibly closed by the remote host.
```
The FileZilla Server gives me the following error:

**Additional Content**
In the example above TLS v1.3 is used. I have also tried setting the Version to TLS v1.2. When I am doing so it takes a lot more files to download until I get an error. Here I get the following error:

This issue also happens with the List command.
I guess the implication is that these “tls.config” settings are within rclone?
Can end users of rclone do anything to set this ServerName setting?
Or is a change in rclone required to enable this?
For me, this error happens when I try rclone sync from Ubuntu pointing to a Windows server running FileZilla server with —ftp-explicit-tls set along with other config all on the command line.
It does not happen when I try the same settings except pointing at Linux servers running PureFTP.
Using passive settings in FileZilla with host name set to the same as the name in the LetsEncrypt certificate, which is the same as the reverse DNS of the sever IP
Maybe there’s another place in FileZilla where I need to set the ServerName?
rclone also works fine connecting to FileZilla but without enabling explict TLS.
Also fine with concurrency set to 1 (was just using default)
Does NOT work when concurrency set to 2
Presumably, rclone is not or cannot share the TLS settings for all connections?
(default concurrency is fine for explict TLS connections to PureFTP servers though, so it's strange it seems to be only FileZilla server to have this problem, though I've only connected to PureFTP and FileZilla so there may be others too)