The result from the test:
Status: Resolving address of kthhub.kth.net
Status: Connecting to 173.188.116.230
Warning: The entered address does not resolve to an IPv6 address.
Status: Connected, waiting for welcome message...
Reply: 220 Serv-U FTP Server v15.1 ready...
Command: CLNT
https://ftptest.net on behalf of 74.218.211.18
Reply: 200 Noted.
Command: AUTH TLS
Reply: 234 AUTH command OK. Initializing SSL connection.
Status: Performing TLS handshake...
Status: TLS handshake successful, verifying certificate...
Status: Received 1 certificates from server.
Status: cert[0]: subject='C=US,ST=OH,L=Saint Paris,O=KTH Parts Industries\5c, Inc.,OU=ISG,CN=kthhub.kth.net' issuer='C=US,ST=OH,L=Saint Paris,O=KTH Parts Industries\5c, Inc.,OU=ISG,CN=kthhub.kth.net'
Command: USER rosewoodmachine
Reply: 331 User name okay, need password.
Command: PASS ********
Reply: 230 User logged in, proceed.
Command: SYST
Reply: 215 UNIX Type: L8
Command: FEAT
Reply: 211-Extensions supported
Reply: UTF8
Reply: OPTS MODE;MLST;UTF8
Reply: CLNT
Reply: CSID Name; Version;
Reply: HOST domain
Reply: SITE PSWD;SET;ZONE;CHMOD;MSG;EXEC;HELP
Reply: AUTH TLS;SSL;TLS-C;TLS-P;
Reply: PBSZ
Reply: PROT
Reply: CCC
Reply: SSCN
Reply: RMDA directoryname
Reply: DSIZ
Reply: AVBL
Reply: EPRT
Reply: EPSV
Reply: MODE Z
Reply: THMB BMP|JPEG|GIF|TIFF|PNG max_width max_height pathname
Reply: REST STREAM
Reply: SIZE
Reply: MDTM
Reply: MDTM YYYYMMDDHHMMSS[+-TZ];filename
Reply: MFMT
Reply: MFCT
Reply: MFF Create;Modify;
Reply: XCRC filename;start;end
Reply: XMD5 filename;start;end
Reply: XSHA1 filename;start;end
Reply: XSHA256 filename;start;end
Reply: XSHA512 filename;start;end
Reply: COMB target;source_list
Reply: MLST Type*;Size*;Create;Modify*;Perm;Win32.ea;Win32.dt;Win32.dl
Reply: 211 End (for details use "HELP commmand" where command is the command of interest)
Command: PBSZ 0
Reply: 200 PBSZ command OK. Protection buffer size set to 0.
Command: PROT P
Reply: 200 PROT command OK. Using private data connection.
Command: PWD
Reply: 257 "/" is current directory.
Status: Current path is /
Command: TYPE I
Reply: 200 Type set to I.
Command: PASV
Reply: 227 Entering Passive Mode (173,188,116,230,35,78)
Command: MLSD
Status: Data connection established, performing TLS handshake...
Status: TLS handshake successful, verifying certificate...
Status: Received 1 certificates from server.
Status: cert[0]: subject='C=US,ST=OH,L=Saint Paris,O=KTH Parts Industries\5c, Inc.,OU=ISG,CN=kthhub.kth.net' issuer='C=US,ST=OH,L=Saint Paris,O=KTH Parts Industries\5c, Inc.,OU=ISG,CN=kthhub.kth.net'
Status: TLS session of transfer connection has been resumed.
Reply: 150 Opening BINARY mode data connection for MLSD.
Listing: Type=dir;Modify=20190117050131.289; from_kth
Listing: Type=dir;Modify=20181221190100.484; to_kth
Reply: 226 Transfer complete. 90 bytes transferred. 0.09 KB/sec.
Status: Success
Results
Your server is working and assorted routers/firewalls have been correctly configured for explicit FTP over TLS as performed by this test. However there have been warnings about compatibility issues, not all users will be able to use your server.
For maximum compatibility, consider resolving these warnings.