SFTP to CoreOS in Netbeans fails

Question

I can connect to my server through the sftp command in the terminal and it works just fine through filezilla as well.

But when I try the connection in netbeans, it fails; output:

Connecting to x.x.x.x port 22
Connection established
Remote version string: SSH-2.0-OpenSSH_6.7
Local version string: SSH-2.0-JSCH-0.1.49
CheckCiphers: aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,3des-ctr,arcfour,arcfour128,arcfour256
aes256-ctr is not available.
aes192-ctr is not available.
aes256-cbc is not available.
aes192-cbc is not available.
arcfour256 is not available.
CheckKexes: diffie-hellman-group14-sha1
diffie-hellman-group14-sha1 is not available.
SSH_MSG_KEXINIT sent
SSH_MSG_KEXINIT received
kex: server: curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1
kex: server: ssh-rsa,ssh-dss,ssh-ed25519
kex: server: aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com
kex: server: aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com
kex: server: 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
kex: server: 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
kex: server: none,zlib@openssh.com
kex: server: none,zlib@openssh.com
kex: server:
kex: server:
kex: client: diffie-hellman-group1-sha1,diffie-hellman-group-exchange-sha1
kex: client: ssh-rsa,ssh-dss
kex: client: aes128-ctr,aes128-cbc,3des-ctr,3des-cbc,blowfish-cbc
kex: client: aes128-ctr,aes128-cbc,3des-ctr,3des-cbc,blowfish-cbc
kex: client: hmac-md5,hmac-sha1,hmac-sha2-256,hmac-sha1-96,hmac-md5-96
kex: client: hmac-md5,hmac-sha1,hmac-sha2-256,hmac-sha1-96,hmac-md5-96
kex: client: none
kex: client: none
kex: client:
kex: client:
Disconnecting from x.x.x.x port 22
QUIT
Goodbye

I have no problem connecting to other servers though netbeans and sftp.

How can I solve the issue and connect to the server?

Answer 1

This is because you don't have any common key exchange method on server and client:

kex: server: curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1

[...]

kex: client: diffie-hellman-group1-sha1,diffie-hellman-group-exchange-sha1

To fix it you need to allow some legacy method on server using KexAlgorithms option in sshd_config or allow some reasonable methods on client (not sure how to do this on JSCH).