Negotiation failed. The connection was closed by the server.

Question

Dim thisSFTP = New Rebex.Net.Sftp
Dim par As New SshParameters
par.HostKeyAlgorithms = SshHostKeyAlgorithm.Any 
par.KeyExchangeAlgorithms = par.KeyExchangeAlgorithms Or SshKeyExchangeAlgorithm.DiffieHellmanGroup1SHA1
thisSFTP.LogWriter = new Rebex.FileLogWriter(FtpDebugFile, Rebex.LogLevel.Debug)
thisSFTP.Connect(Instance.remoteHost, Instance.remoteHostPort, par)

Answer 1

par.PreferredHostKeyAlgorithm = SshHostKeyAlgorithm.RSA

Comments

Thank you for sharing VERBOSE log. It showed that the server closed the connection immediately after receiving initial SSH_MSG_KEXINIT.
Can you please share here (or send to support@rebex.net) VERBOSE log from the working 2017r1 version? So we can compare those two. It will be very helpful. Thank you.

---

2017R1 version

>11:34:58.936 Info Info: Connecting to 10.35.81.97:22 using Sftp 3.0.6249.0.
>11:34:59.064 Verbose SSH: Sending data:
>0000 |53-53-48-2D-32-2E-30-2D 52-65-62-65-78-53-53-48| SSH-2.0-RebexSSH
>0010 |5F-33-2E-30-2E-36-32-34 39-2E-30-0D-0A         | _3.0.6249.0..
>11:34:59.296 Verbose SSH: Received data:
>0000 |53-53-48-2D-32-2E-30-2D 4F-70-65-6E-53-53-48-5F| SSH-2.0-OpenSSH_
>0010 |36-2E-36-0D-0A                                 | 6.6..
>11:34:59.327 Debug SSH: Server is 'SSH-2.0-OpenSSH_6.6'.
>11:34:59.374 Info SSH: Negotiation started.
>11:34:59.389 Verbose SSH: Received packet SSH_MSG_KEXINIT (1342 bytes).
>0000 |14-E0-24-B9-D7-D0-72-30 55-C4-E7-4C-22-CC-8A-41| ..$...r0U..L"..A
>0010 |A2-00-00-00-59-64-69-66 66-69-65-2D-68-65-6C-6C| ....Ydiffie-hell
>0020 |6D-61-6E-2D-67-72-6F-75 70-2D-65-78-63-68-61-6E| man-group-exchan
>0030 |67-65-2D-73-68-61-31-2C 64-69-66-66-69-65-2D-68| ge-sha1,diffie-h
>0040 |65-6C-6C-6D-61-6E-2D-67 72-6F-75-70-31-34-2D-73| ellman-group14-s
>0050 |68-61-31-2C-64-69-66-66 69-65-2D-68-65-6C-6C-6D| ha1,diffie-hellm
>0060 |61-6E-2D-67-72-6F-75-70 31-2D-73-68-61-31-00-00| an-group1-sha1..
>0070 |00-1B-73-73-68-2D-72-73 61-2C-73-73-68-2D-64-73| ..ssh-rsa,ssh-ds
>0080 |73-2C-73-73-68-2D-65-64 32-35-35-31-39-00-00-00| s,ssh-ed25519...
>0090 |BB-61-65-73-31-32-38-2D 63-74-72-2C-61-65-73-31| .aes128-ctr,aes1
>00A0 |39-32-2D-63-74-72-2C-61 65-73-32-35-36-2D-63-74| 92-ctr,aes256-ct
>00B0 |72-2C-61-72-63-66-6F-75 72-32-35-36-2C-61-72-63| r,arcfour256,arc
>00C0 |66-6F-75-72-31-32-38-2C 63-68-61-63-68-61-32-30| four128,chacha20
>00D0 |2D-70-6F-6C-79-31-33-30 35-40-6F-70-65-6E-73-73| -poly1305@openss
>00E0 |68-2E-63-6F-6D-2C-61-65 73-31-32-38-2D-63-62-63| h.com,aes128-cbc
>00F0 |2C-33-64-65-73-2D-63-62 63-2C-62-6C-6F-77-66-69| ,3des-cbc,blowfi
>0100 |73-68-2D-63-62-63-2C-63 61-73-74-31-32-38-2D-63| sh-cbc,cast128-c
>0110 |62-63-2C-61-65-73-31-39 32-2D-63-62-63-2C-61-65| bc,aes192-cbc,ae
>0120 |73-32-35-36-2D-63-62-63 2C-61-72-63-66-6F-75-72| s256-cbc,arcfour
>0130 |2C-72-69-6A-6E-64-61-65 6C-2D-63-62-63-40-6C-79| ,rijndael-cbc@ly
>0140 |73-61-74-6F-72-2E-6C-69 75-2E-73-65-00-00-00-BB| sator.liu.se....
>0150 |61-65-73-31-32-38-2D-63 74-72-2C-61-65-73-31-39| aes128-ctr,aes19
>0160 |32-2D-63-74-72-2C-61-65 73-32-35-36-2D-63-74-72| 2-ctr,aes256-ctr
>0170 |2C-61-72-63-66-6F-75-72 32-35-36-2C-61-72-63-66| ,arcfour256,arcf
>0180 |6F-75-72-31-32-38-2C-63 68-61-63-68-61-32-30-2D| our128,chacha20-
>0190 |70-6F-6C-79-31-33-30-35 40-6F-70-65-6E-73-73-68| poly1305@openssh
>01A0 |2E-63-6F-6D-2C-61-65-73 31-32-38-2D-63-62-63-2C| .com,aes128-cbc,
>01B0 |33-64-65-73-2D-63-62-63 2C-62-6C-6F-77-66-69-73| 3des-cbc,blowfis
>01C0 |68-2D-63-62-63-2C-63-61 73-74-31-32-38-2D-63-62| h-cbc,cast128-cb
>01D0 |63-2C-61-65-73-31-39-32 2D-63-62-63-2C-61-65-73| c,aes192-cbc,aes
>01E0 |32-35-36-2D-63-62-63-2C 61-72-63-66-6F-75-72-2C| 256-cbc,arcfour,
>01F0 |72-69-6A-6E-64-61-65-6C 2D-63-62-63-40-6C-79-73| rijndael-cbc@lys
>0200 |61-74-6F-72-2E-6C-69-75 2E-73-65-00-00-01-76-68| ator.liu.se...vh
>0210 |6D-61-63-2D-6D-64-35-2D 65-74-6D-40-6F-70-65-6E| mac-md5-etm@open
>0220 |73-73-68-2E-63-6F-6D-2C 68-6D-61-63-2D-73-68-61| ssh.com,hmac-sha
>0230 |31-2D-65-74-6D-40-6F-70 65-6E-73-73-68-2E-63-6F| 1-etm@openssh.co
>0240 |6D-2C-75-6D-61-63-2D-36 34-2D-65-74-6D-40-6F-70| m,umac-64-etm@op
>0250 |65-6E-73-73-68-2E-63-6F 6D-2C-75-6D-61-63-2D-31| enssh.com,umac-1
>0260 |32-38-2D-65-74-6D-40-6F 70-65-6E-73-73-68-2E-63| 28-etm@openssh.c
>0270 |6F-6D-2C-68-6D-61-63-2D 73-68-61-32-2D-32-35-36| om,hmac-sha2-256
>0280 |2D-65-74-6D-40-6F-70-65 6E-73-73-68-2E-63-6F-6D| -etm@openssh.com
>0290 |2C-68-6D-61-63-2D-73-68 61-32-2D-35-31-32-2D-65| ,hmac-sha2-512-e
>02A0 |74-6D-40-6F-70-65-6E-73 73-68-2E-63-6F-6D-2C-68| tm@openssh.com,h
>02B0 |6D-61-63-2D-72-69-70-65 6D-64-31-36-30-2D-65-74| mac-ripemd160-et
>02C0 |6D-40-6F-70-65-6E-73-73 68-2E-63-6F-6D-2C-68-6D| m@openssh.com,hm
>02D0 |61-63-2D-73-68-61-31-2D 39-36-2D-65-74-6D-40-6F| ac-sha1-96-etm@o
>02E0 |70-65-6E-73-73-68-2E-63 6F-6D-2C-68-6D-61-63-2D| penssh.com,hmac-
>02F0 |6D-64-35-2D-39-36-2D-65 74-6D-40-6F-70-65-6E-73| md5-96-etm@opens
>0300 |73-68-2E-63-6F-6D-2C-68 6D-61-63-2D-6D-64-35-2C| sh.com,hmac-md5,
>0310 |68-6D-61-63-2D-73-68-61 31-2C-75-6D-61-63-2D-36| hmac-sha1,umac-6
>0320 |34-40-6F-70-65-6E-73-73 68-2E-63-6F-6D-2C-75-6D| 4@openssh.com,um
>0330 |61-63-2D-31-32-38-40-6F 70-65-6E-73-73-68-2E-63| ac-128@openssh.c
>0340 |6F-6D-2C-68-6D-61-63-2D 72-69-70-65-6D-64-31-36| om,hmac-ripemd16
>0350 |30-2C-68-6D-61-63-2D-72 69-70-65-6D-64-31-36-30| 0,hmac-ripemd160
>0360 |40-6F-70-65-6E-73-73-68 2E-63-6F-6D-2C-68-6D-61| @openssh.com,hma
>0370 |63-2D-73-68-61-31-2D-39 36-2C-68-6D-61-63-2D-6D| c-sha1-96,hmac-m
>0380 |64-35-2D-39-36-00-00-01 76-68-6D-61-63-2D-6D-64| d5-96...vhmac-md
>0390 |35-2D-65-74-6D-40-6F-70 65-6E-73-73-68-2E-63-6F| 5-etm@openssh.co
>03A0 |6D-2C-68-6D-61-63-2D-73 68-61-31-2D-65-74-6D-40| m,hmac-sha1-etm@
>03B0 |6F-70-65-6E-73-73-68-2E 63-6F-6D-2C-75-6D-61-63| openssh.com,umac
>03C0 |2D-36-34-2D-65-74-6D-40 6F-70-65-6E-73-73-68-2E| -64-etm@openssh.
>03D0 |63-6F-6D-2C-75-6D-61-63 2D-31-32-38-2D-65-74-6D| com,umac-128-etm
>03E0 |40-6F-70-65-6E-73-73-68 2E-63-6F-6D-2C-68-6D-61| @openssh.com,hma
>03F0 |63-2D-73-68-61-32-2D-32 35-36-2D-65-74-6D-40-6F| c-sha2-256-etm@o
>0400 |70-65-6E-73-73-68-2E-63 6F-6D-2C-68-6D-61-63-2D| penssh.com,hmac-
>0410 |73-68-61-32-2D-35-31-32 2D-65-74-6D-40-6F-70-65| sha2-512-etm@ope
>0420 |6E-73-73-68-2E-63-6F-6D 2C-68-6D-61-63-2D-72-69| nssh.com,hmac-ri
>0430 |70-65-6D-64-31-36-30-2D 65-74-6D-40-6F-70-65-6E| pemd160-etm@open
>0440 |73-73-68-2E-63-6F-6D-2C 68-6D-61-63-2D-73-68-61| ssh.com,hmac-sha
>0450 |31-2D-39-36-2D-65-74-6D 40-6F-70-65-6E-73-73-68| 1-96-etm@openssh
>0460 |2E-63-6F-6D-2C-68-6D-61 63-2D-6D-64-35-2D-39-36| .com,hmac-md5-96
>0470 |2D-65-74-6D-40-6F-70-65 6E-73-73-68-2E-63-6F-6D| -etm@openssh.com
>0480 |2C-68-6D-61-63-2D-6D-64 35-2C-68-6D-61-63-2D-73| ,hmac-md5,hmac-s
>0490 |68-61-31-2C-75-6D-61-63 2D-36-34-40-6F-70-65-6E| ha1,umac-64@open
>04A0 |73-73-68-2E-63-6F-6D-2C 75-6D-61-63-2D-31-32-38| ssh.com,umac-128
>04B0 |40-6F-70-65-6E-73-73-68 2E-63-6F-6D-2C-68-6D-61| @openssh.com,hma
>04C0 |63-2D-72-69-70-65-6D-64 31-36-30-2C-68-6D-61-63| c-ripemd160,hmac
>04D0 |2D-72-69-70-65-6D-64-31 36-30-40-6F-70-65-6E-73| -ripemd160@opens
>04E0 |73-68-2E-63-6F-6D-2C-68 6D-61-63-2D-73-68-61-31| sh.com,hmac-sha1
>04F0 |2D-39-36-2C-68-6D-61-63 2D-6D-64-35-2D-39-36-00| -96,hmac-md5-96.
>0500 |00-00-15-6E-6F-6E-65-2C 7A-6C-69-62-40-6F-70-65| ...none,zlib@ope
>0510 |6E-73-73-68-2E-63-6F-6D 00-00-00-15-6E-6F-6E-65| nssh.com....none
>0520 |2C-7A-6C-69-62-40-6F-70 65-6E-73-73-68-2E-63-6F| ,zlib@openssh.co
>0530 |6D-00-00-00-00-00-00-00 00-00-00-00-00-00      | m.............

---

2017 part2

>11:34:59.467 Verbose SSH: Sending packet SSH_MSG_KEXINIT (913 bytes).
>0000 |14-40-5E-50-C5-C6-F9-43 1B-6B-7D-7C-21-F9-43-64| .@^P...C.k}|!.Cd
>0010 |5B-00-00-00-D0-64-69-66 66-69-65-2D-68-65-6C-6C| [....diffie-hell
>0020 |6D-61-6E-2D-67-72-6F-75 70-2D-65-78-63-68-61-6E| man-group-exchan
>0030 |67-65-2D-73-68-61-32-35 36-2C-64-69-66-66-69-65| ge-sha256,diffie
>0040 |2D-68-65-6C-6C-6D-61-6E 2D-67-72-6F-75-70-31-34| -hellman-group14
>0050 |2D-73-68-61-32-35-36-2C 64-69-66-66-69-65-2D-68| -sha256,diffie-h
>0060 |65-6C-6C-6D-61-6E-2D-67 72-6F-75-70-31-35-2D-73| ellman-group15-s
>0070 |68-61-35-31-32-2C-64-69 66-66-69-65-2D-68-65-6C| ha512,diffie-hel
>0080 |6C-6D-61-6E-2D-67-72-6F 75-70-31-36-2D-73-68-61| lman-group16-sha
>0090 |35-31-32-2C-64-69-66-66 69-65-2D-68-65-6C-6C-6D| 512,diffie-hellm
>00A0 |61-6E-2D-67-72-6F-75-70 2D-65-78-63-68-61-6E-67| an-group-exchang
>00B0 |65-2D-73-68-61-31-2C-64 69-66-66-69-65-2D-68-65| e-sha1,diffie-he
>00C0 |6C-6C-6D-61-6E-2D-67-72 6F-75-70-31-34-2D-73-68| llman-group14-sh
>00D0 |61-31-2C-65-63-64-68-2D 73-68-61-32-2D-6E-69-73| a1,ecdh-sha2-nis
>00E0 |74-70-32-35-36-00-00-00 93-73-73-68-2D-64-73-73| tp256....ssh-dss
>00F0 |2C-72-73-61-2D-73-68-61 32-2D-32-35-36-2C-73-73| ,rsa-sha2-256,ss
>0100 |68-2D-72-73-61-2D-73-68 61-32-35-36-40-73-73-68| h-rsa-sha256@ssh
>0110 |2E-63-6F-6D-2C-72-73-61 2D-73-68-61-32-2D-35-31| .com,rsa-sha2-51
>0120 |32-2C-73-73-68-2D-72-73 61-2C-78-35-30-39-76-33| 2,ssh-rsa,x509v3
>0130 |2D-73-69-67-6E-2D-72-73 61-2D-73-68-61-32-35-36| -sign-rsa-sha256
>0140 |40-73-73-68-2E-63-6F-6D 2C-78-35-30-39-76-33-2D| @ssh.com,x509v3-
>0150 |73-69-67-6E-2D-72-73-61 2C-78-35-30-39-76-33-2D| sign-rsa,x509v3-
>0160 |73-69-67-6E-2D-64-73-73 2C-65-63-64-73-61-2D-73| sign-dss,ecdsa-s
>0170 |68-61-32-2D-6E-69-73-74 70-32-35-36-00-00-00-B9| ha2-nistp256....
>0180 |61-65-73-32-35-36-2D-63 74-72-2C-61-65-73-31-39| aes256-ctr,aes19
>0190 |32-2D-63-74-72-2C-61-65 73-31-32-38-2D-63-74-72| 2-ctr,aes128-ctr
>01A0 |2C-61-65-73-32-35-36-2D 63-62-63-2C-61-65-73-31| ,aes256-cbc,aes1
>01B0 |39-32-2D-63-62-63-2C-61 65-73-31-32-38-2D-63-62| 92-cbc,aes128-cb
>01C0 |63-2C-33-64-65-73-2D-63 74-72-2C-33-64-65-73-2D| c,3des-ctr,3des-
>01D0 |63-62-63-2C-74-77-6F-66 69-73-68-32-35-36-2D-63| cbc,twofish256-c
>01E0 |74-72-2C-74-77-6F-66-69 73-68-31-39-32-2D-63-74| tr,twofish192-ct
>01F0 |72-2C-74-77-6F-66-69-73 68-31-32-38-2D-63-74-72| r,twofish128-ctr
>0200 |2C-74-77-6F-66-69-73-68 32-35-36-2D-63-62-63-2C| ,twofish256-cbc,
>0210 |74-77-6F-66-69-73-68-31 39-32-2D-63-62-63-2C-74| twofish192-cbc,t
>0220 |77-6F-66-69-73-68-31-32 38-2D-63-62-63-2C-74-77| wofish128-cbc,tw
>0230 |6F-66-69-73-68-2D-63-62 63-00-00-00-B9-61-65-73| ofish-cbc....aes
>0240 |32-35-36-2D-63-74-72-2C 61-65-73-31-39-32-2D-63| 256-ctr,aes192-c
>0250 |74-72-2C-61-65-73-31-32 38-2D-63-74-72-2C-61-65| tr,aes128-ctr,ae
>0260 |73-32-35-36-2D-63-62-63 2C-61-65-73-31-39-32-2D| s256-cbc,aes192-
>0270 |63-62-63-2C-61-65-73-31 32-38-2D-63-62-63-2C-33| cbc,aes128-cbc,3
>0280 |64-65-73-2D-63-74-72-2C 33-64-65-73-2D-63-62-63| des-ctr,3des-cbc
>0290 |2C-74-77-6F-66-69-73-68 32-35-36-2D-63-74-72-2C| ,twofish256-ctr,
>02A0 |74-77-6F-66-69-73-68-31 39-32-2D-63-74-72-2C-74| twofish192-ctr,t
>02B0 |77-6F-66-69-73-68-31-32 38-2D-63-74-72-2C-74-77| wofish128-ctr,tw
>02C0 |6F-66-69-73-68-32-35-36 2D-63-62-63-2C-74-77-6F| ofish256-cbc,two
>02D0 |66-69-73-68-31-39-32-2D 63-62-63-2C-74-77-6F-66| fish192-cbc,twof
>02E0 |69-73-68-31-32-38-2D-63 62-63-2C-74-77-6F-66-69| ish128-cbc,twofi
>02F0 |73-68-2D-63-62-63-00-00 00-25-68-6D-61-63-2D-73| sh-cbc...%hmac-s
>0300 |68-61-32-2D-32-35-36-2C 68-6D-61-63-2D-73-68-61| ha2-256,hmac-sha
>0310 |32-2D-35-31-32-2C-68-6D 61-63-2D-73-68-61-31-00| 2-512,hmac-sha1.
>0320 |00-00-25-68-6D-61-63-2D 73-68-61-32-2D-32-35-36| ..%hmac-sha2-256
>0330 |2C-68-6D-61-63-2D-73-68 61-32-2D-35-31-32-2C-68| ,hmac-sha2-512,h
>0340 |6D-61-63-2D-73-68-61-31 00-00-00-1A-6E-6F-6E-65| mac-sha1....none
>0350 |2C-7A-6C-69-62-2C-7A-6C 69-62-40-6F-70-65-6E-73| ,zlib,zlib@opens
>0360 |73-68-2E-63-6F-6D-00-00 00-1A-6E-6F-6E-65-2C-7A| sh.com....none,z
>0370 |6C-69-62-2C-7A-6C-69-62 40-6F-70-65-6E-73-73-68| lib,zlib@openssh
>0380 |2E-63-6F-6D-00-00-00-00 00-00-00-00-00-00-00-00| .com............
>0390 |00                                             | .
>11:34:59.530 Debug SSH: Group exchange.
>11:34:59.545 Verbose SSH: Sending packet SSH_MSG_KEX_DH_GEX_REQUEST (13 bytes).
>0000 |22-00-00-04-00-00-00-08 00-00-00-10-00         | "............
>11:34:59.639 Verbose SSH: Received packet SSH_MSG_KEX_31 (267 bytes).
>0000 |1F-00-00-01-01-00-DD-20 47-CB-DB-B6-F8-E9-19-BC| ....... G.......
>0010 |63-DE-88-5B-34-D0-FD-6E 3D-B2-88-7D-8B-46-FE-24| c..[4..n=..}.F.$
>0020 |98-86-AC-ED-6B-46-DF-CD 55-53-16-81-85-FD-37-61| ....kF..US....7a
>0030 |22-17-1C-D8-92-7E-60-12 0F-A8-D0-1F-01-D0-3E-58| "....~`.......>X
>0040 |28-1F-EA-9A-1A-BE-97-63 1C-82-8E-41-81-5F-34-FD| (......c...A._4.
>0050 |CD-F7-87-41-9F-E1-3A-31 37-64-9A-A9-3D-25-84-23| ...A..:17d..=%.#
>0060 |0D-F5-F2-4B-5C-00-C8-8B 7D-7D-E4-36-76-93-42-8C| ...K\...}}.6v.B.
>0070 |73-03-76-F2-18-A5-3E-85 3B-08-51-BA-B7-C5-3C-15| s.v...>.;.Q...<.
>0080 |DA-78-39-CB-E1-28-5D-B6 3F-6F-A4-5C-1B-B5-9F-E1| .x9..(].?o.\....
>0090 |C5-BB-91-8F-0F-84-59-D7 EF-60-AC-FF-5C-0F-A0-F3| ......Y..`..\...
>00A0 |FC-AD-1C-5F-4C-E4-41-6D 4F-4B-36-B0-5C-DC-EB-E4| ..._L.AmOK6.\...
>00B0 |FB-87-9E-95-84-7E-FB-C6 44-9C-D1-90-24-88-43-BC| .....~..D...$.C.
>00C0 |7E-DB-14-5F-BF-C4-ED-BB 1A-3C-95-92-98-F0-8F-3B| ~.._.....<.....;
>00D0 |A2-CF-BE-23-1B-BE-20-4B E6-F9-06-20-9D-28-BD-48| ...#.. K... .(.H
>00E0 |20-AB-3E-7B-E9-6C-26-AE 8A-80-9A-DD-8D-1A-5A-0B|  .>{.l&.......Z.
>00F0 |00-8E-95-70-FA-4C-46-97 E1-16-B8-11-98-92-C6-04| ...p.LF.........
>0100 |29-36-84-4F-AB-5B-00-00 00-01-02               | )6.O.[.....
>11:34:59.655 Debug SSH: Negotiating key.
>11:34:59.702 Debug SSH: Received 2048-bit Diffie-Hellman prime (minimum allowed size is 1024 bits).
>11:34:59.717 Verbose SSH: Sending packet SSH_MSG_KEX_DH_GEX_INIT (262 bytes).
>0000 |20-00-00-01-01-00-AB-78 C3-78-98-23-CB-34-B6-ED|  ......x.x.#.4..
>0010 |8B-6D-2C-35-B3-8B-80-8E A8-0D-69-47-F2-97-23-1A| .m,5......iG..#.
>0020 |48-F7-49-4C-AD-5E-88-FF FC-1C-0E-9B-EB-26-CA-96| H.IL.^.......&..
>0030 |0E-72-D5-42-81-08-CC-D4 A9-7B-1B-1C-0F-EC-79-FA| .r.B.....{....y.
>0040 |1C-F0-0F-2D-A4-73-50-5A CE-1A-EB-07-99-09-AA-00| ...-.sPZ........
>0050 |66-FE-E0-F6-7C-F2-1D-0B 3A-A3-86-8D-1A-C4-17-E3| f...|...:.......
>0060 |B7-46-02-8B-A1-E5-78-B1 9F-E0-E7-81-25-C0-2A-D1| .F....x.....%.*.
>0070 |F0-02-D7-51-C3-C3-F2-04 6C-ED-21-32-2B-E5-64-A2| ...Q....l.!2+.d.
>0080 |2C-60-7B-8D-9D-2D-A1-D7 BA-14-92-59-4C-7F-69-20| ,`{..-.....YL.i
> 0090 |E3-68-A4-F8-B7-2E-CD-14 58-AA-A8-B8-7A-A3-F2-B7| .h......X...z...
>00A0 |63-3C-34-72-00-38-84-D5 64-79-DA-8F-86-40-A4-AC| c<4r.8..dy...@..
>00B0 |22-BF-1C-50-4F-F5-E4-80 2F-A5-E1-58-F6-96-4E-6E| "..PO.../..X..Nn
>00C0 |7E-43-4C-01-14-E0-36-51 A4-4A-5C-BC-11-98-C8-C4| ~CL...6Q.J\.....
>00D0 |81-E4-91-A6-58-F7-5A-B5 C0-D7-28-06-13-C9-94-02| ....X.Z...(.....
>00E0 |EB-3C-E5-9A-5E-CA-35-F2 6E-E9-BB-3F-BB-5C-3A-E3| .<..^.5.n..?.\:.
>00F0 |C8-81-A9-FA-52-0F-58-55 30-B9-27-30-E6-17-48-D1| ....R.XU0.'0..H.
>0100 |08-B5-F8-3F-0B-DC

---

2017R1 part 3

>11:34:59.905 Verbose SSH: Received packet SSH_MSG_KEX_DH_GEX_REPLY (758 bytes).
>0000 |21-00-00-01-B1-00-00-00 07-73-73-68-2D-64-73-73| !........ssh-dss
>0010 |00-00-00-81-00-C3-55-FF 5E-45-62-88-5A-BE-7F-4D| ......U.^Eb.Z..M
>0020 |4F-34-DB-F3-B7-55-FC-52 7F-09-1B-DD-D9-E0-5F-2D| O4...U.R......_-
>0030 |99-8C-A3-F5-57-0F-E3-6C 45-FA-13-17-22-DB-56-A8| ....W..lE...".V.
>0040 |52-68-FB-BA-06-37-4E-21 05-44-09-4C-CD-A7-5F-6A| Rh...7N!.D.L.._j
>0050 |9D-30-A3-3C-00-05-D3-32 E0-C0-F0-ED-65-96-2F-C9| .0.<...2....e./.
>0060 |80-E0-6D-7C-82-A3-EA-A5 9D-3E-41-61-5F-40-63-35| ..m|.....>Aa_@c5
>0070 |EC-ED-A2-47-0E-65-AB-93 2F-20-C7-B4-2F-8E-82-9A| ...G.e../ ../...
>0080 |27-44-3F-3F-FE-C3-AA-A6 47-EB-5F-77-18-EC-E2-6D| 'D??....G._w...m
>0090 |93-FD-14-A6-5B-00-00-00 15-00-D9-F0-D6-C8-78-E2| ....[.........x.
>00A0 |8F-02-B0-D8-48-47-71-61 D5-89-BD-07-68-D7-00-00| ....HGqa....h...
>00B0 |00-80-5B-A3-36-DF-AA-26 6D-DD-17-8D-A0-74-9B-7C| ..[.6..&m....t.|
>00C0 |A9-AA-27-07-20-65-D3-A3 EE-FB-BE-4E-DC-B8-6D-7A| ..'. e.....N..mz
>00D0 |41-3F-05-9A-DF-76-7A-2F 0D-C8-76-33-45-DC-56-5E| A?...vz/..v3E.V^
>00E0 |C7-E8-A5-07-C9-32-60-09 14-09-6C-5C-D6-D4-FD-3E| .....2`...l\...>
>00F0 |B7-5A-6E-09-CC-42-72-D0 4F-20-D4-90-12-A8-00-EE| .Zn..Br.O ......
>0100 |E4-92-2D-63-AF-9F-4A-8D 4B-C9-CF-87-2C-FC-12-20| ..-c..J.K...,..
> 0110 |F1-BC-DB-24-51-DE-74-3E BF-AF-41-AB-5B-8F-5E-F7| ...$Q.t>..A.[.^.
>0120 |13-E7-80-EF-D5-E4-D3-EE 36-E1-99-64-AF-1A-81-D6| ........6..d....
>0130 |C3-20-00-00-00-80-0E-EA B0-BF-7B-80-B1-73-6A-BC| . ........{..sj.
>0140 |36-69-8F-CF-FA-35-3C-F0 BE-85-34-0F-00-E1-FA-15| 6i...5<...4.....
>0150 |3B-40-CD-23-D7-8A-9E-A1 EE-DC-32-4B-08-4B-1A-81| ;@.#......2K.K..
>0160 |71-6D-BA-9E-AC-77-6B-32 0B-A5-14-5D-C9-3E-33-4C| qm...wk2...].>3L
>0170 |A3-39-E8-5C-98-3F-EB-5A 39-46-C9-D0-70-9B-F2-93| .9.\.?.Z9F..p...
>0180 |85-79-C4-E5-97-CF-F6-2D 3F-40-CC-34-98-B6-18-F2| .y.....-?@.4....
>0190 |FF-E3-39-1E-DA-0A-B1-06 80-3F-D2-CD-9E-8F-5D-7C| ..9......?....]|
>01A0 |98-67-A5-61-AF-D0-30-D9 F9-57-1D-56-AE-EA-43-B1| .g.a..0..W.V..C.
>01B0 |22-7D-C8-D3-F1-A5-00-00 01-01-00-B9-FC-BF-EA-60| "}.............`
>01C0 |B1-B6-3A-00-14-F8-74-22 CE-2D-5B-FD-D7-B1-AD-72| ..:...t".-[....r
>01D0 |94-D5-4A-63-37-23-F5-95 38-EE-D1-E6-75-EF-CF-64| ..Jc7#..8...u..d
>01E0 |60-AA-A1-1B-99-D5-F1-BD C8-93-B1-61-43-D3-5D-53| `..........aC.]S
>01F0 |BE-15-8E-BF-7B-25-DB-3A 6C-84-5D-F3-74-2F-3C-87| ....{%.:l.].t/<.
>0200 |27-8C-2A-04-65-13-05-10 AA-77-63-7A-32-F8-86-AA| '.*.e....wcz2...
>0210 |08-D0-C1-CB-51-20-5E-DE 3E-D6-3A-D8-AD-52-2F-48| ....Q ^.>.:..R/H
>0220 |36-5A-F6-97-E5-C9-DB-F5 23-41-65-EC-EC-E0-1B-16| 6Z......#Ae.....
>0230 |66-46-21-C7-01-68-58-36 3F-BF-4F-07-5F-88-12-7A| fF!..hX6?.O._..z
>0240 |72-38-29-BC-29-62-F5-FD A9-2D-EE-16-FF-6C-E9-80| r8).)b...-...l..
>0250 |18-3F-AA-62-1C-73-9D-53 6D-6E-59-CD-73-AD-29-A8| .?.b.s.SmnY.s.).
>0260 |EE-DD-90-9E-62-F2-6B-A3 8A-1C-8F-AF-83-6F-BA-B2| ....b.k......o..
>0270 |8F-5E-A2-20-E7-96-3F-6F D3-AE-15-92-D2-C0-98-D3| .^. ..?o........
>0280 |E2-0D-3C-E3-3E-0F-2A-09 FB-0B-8F-66-6A-87-76-CA| ..<.>.*....fj.v.
>0290 |FF-08-1B-45-D7-91-9D-9B 28-8F-D7-8D-08-6E-4F-22| ...E....(....nO"
>02A0 |C6-43-A0-F2-BB-8C-54-26 62-2A-42-2B-FB-F7-AD-61| .C....T&b*B+...a
>02B0 |2D-20-E9-C6-7B-61-CF-BA 5F-E1-27-00-00-00-37-00| - ..{a.._.'...7.
>02C0 |00-00-07-73-73-68-2D-64 73-73-00-00-00-28-76-B7| ...ssh-dss...(v.
>02D0 |4F-01-31-FB-1F-94-B2-76 2F-45-0B-4C-11-C6-08-C5| O.1....v/E.L....
>02E0 |30-D0-61-9A-20-71-E0-AA F0-52-DE-5D-D4-4E-2D-1B| 0.a. q...R.].N-.
>02F0 |C6-85-98-64-8B-61                              | ...d.a
>11:34:59.920 Verbose SSH: Received packet SSH_MSG_NEWKEYS (1 bytes).
>0000 |15                                             | .
>11:34:59.983 Debug SSH: Validating signature.
>11:35:00.061 Verbose SSH: Sending packet SSH_MSG_NEWKEYS (1 bytes).
>0000 |15                                             | .
>11:35:00.092 Info SSH: Negotiation finished.

---

Thank you for the log. I have noticed, that in version 2017r1, you did not use the diffie-hellman-group1-sha1. It corresponds to this setting:

par.KeyExchangeAlgorithms = par.KeyExchangeAlgorithms Or SshKeyExchangeAlgorithm.DiffieHellmanGroup1SHA1

There are other differences, we will look at those.

In the mean time, can you please disable adding DiffieHellmanGroup1SHA1 in the newer version (2018r2 or 2019r1). Just comment out the mentioned line for setting the par.KeyExchangeAlgorithms.
It is possible that the server has some issue with this legacy algorithm.

Answer 2

Dim thisSFTP = New Rebex.Net.Sftp

Dim par = thisSFTP.Settings.SshParameters
par.SetKeyExchangeAlgorithms("diffie-hellman-group-exchange-sha256",
                                "diffie-hellman-group14-sha256",
                                "diffie-hellman-group15-sha512",
                                "diffie-hellman-group16-sha512",
                                "diffie-hellman-group-exchange-sha1",
                                "diffie-hellman-group14-sha1",
                                "ecdh-sha2-nistp256")
par.SetHostKeyAlgorithms("ssh-dss",
                            "rsa-sha2-256",
                            "ssh-rsa-sha256@ssh.com",
                            "rsa-sha2-512",
                            "ssh-rsa",
                            "x509v3-sign-rsa-sha256@ssh.com",
                            "x509v3-sign-rsa",
                            "x509v3-sign-dss",
                            "ecdsa-sha2-nistp256")
par.SetEncryptionAlgorithms("aes256-ctr",
                                "aes192-ctr",
                                "aes128-ctr",
                                "aes256-cbc",
                                "aes192-cbc",
                                "aes128-cbc",
                                "3des-ctr",
                                "3des-cbc",
                                "twofish256-ctr",
                                "twofish192-ctr",
                                "twofish128-ctr",
                                "twofish256-cbc",
                                "twofish192-cbc",
                                "twofish128-cbc",
                                "twofish-cbc")
par.SetMacAlgorithms("hmac-sha2-256",
                    "hmac-sha2-512",
                    "hmac-sha1")

thisSFTP.LogWriter = new Rebex.FileLogWriter(FtpDebugFile, Rebex.LogLevel.Debug)
thisSFTP.Connect(Instance.remoteHost, Instance.remoteHostPort)