When I connect to SFTP in C# I get the following exception message from a particular host:
KeyExchange response is not SSH_MSG_KEX_DH_GEX_GROUP but SSH_MSG_UNIMPLEMENTED
The last bit of the debug log is as follows:
DEBUG [AbstractKeyExchanger] 10 May 2019 15:09:36.227 : Decided hostkey alg= RSA
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.227 : Remote Cipher CS=aes128-ctr,aes192-ctr,aes256-ctr
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : Decided Cipher C->S= AES_CTR_128
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : Remote Cipher SC=aes128-ctr,aes192-ctr,aes256-ctr
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : Decided Cipher S->C= AES_CTR_128
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : Remote MAC CS=umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : Decided MAC C->S= HMAC_SHA1
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : Remote MAC SC=umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : Decided MAC S->C= HMAC_SHA1
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : Remote Comp CS=none,zlib@openssh.com
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : Decided Comp C->S=None
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : Remote Comp SC=none,zlib@openssh.com
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : Decided Comp S->C=None
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : first_kex_packet_follows=False
DEBUG [AbstractKeyExchanger] 10 May 2019 15:09:36.228 : Processed SSH_MSG_KEXINIT reply
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.228 : Sending SSH_MSG_KEX_DH_GEX_REQUEST_OLD
DEBUG [AbstractKeyExchanger] 10 May 2019 15:09:36.229 : DH_PREFERRED_GROUP_SIZE=1024
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.229 : Sent SSH_MSG_KEX_DH_GEX_REQUEST_OLD
DEBUG [SSH2Connection] 10 May 2019 15:09:36.229 : Waiting for packet
DEBUG [PlainSocket] 10 May 2019 15:09:36.365 : FTPConnection.1 RepeatCallback received 16 bytes
DEBUG [SSH2Connection] 10 May 2019 15:09:36.365 : Packet arrived
DEBUG [ClientKeyExchanger] 10 May 2019 15:09:36.365 : Processing SSH_MSG_KEX_DH_GEX_GROUP reply
