java.io.IOException: Key exchange was not finished, connection is closed.

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Solve 'java.io.IOException: Key exchange was not finished, connection is closed' exception and 'java.io.IOException: Cannot negotiate, proposals do not match.' exception with REHL 9 instance in AWS ..

This page tells you how to solve the "java.io.IOException: Key exchange was not finished, connection is closed" exception or "Caused by: java.io.IOException: Cannot negotiate, proposals do not match." issue when user is trying to connect redhat linux (RHEL) 9 from a java clinet program over SSH using ganymed library/jar and authenticated by key .

If you trying to connect Red Hat Linux (RHEL) centos 9 over SSH using ganymed-ssh-2 library and getting following exception, you can solve it by following change..
Key exchange was not finished, connection is closed with ganymed-ssh-2 and Cisco Confd
Exception:

Exception in thread "main" java.io.IOException: Key exchange was not finished, connection is closed.
	at ch.ethz.ssh2.transport.KexManager.getOrWaitForConnectionInfo(KexManager.java:76)
	at ch.ethz.ssh2.transport.TransportManager.getConnectionInfo(TransportManager.java:169)
	at ch.ethz.ssh2.Connection.connect(Connection.java:759)
	at ch.ethz.ssh2.Connection.connect(Connection.java:628)
	at comz.ConnectRemoteAndExecute.connectAndExecute(ConnectRemoteAndExecute.java:33)
	at comz.ConnectRemoteAndExecute.main(ConnectRemoteAndExecute.java:16)
Caused by: java.io.IOException: Cannot negotiate, proposals do not match.
	at ch.ethz.ssh2.transport.ClientKexManager.handleMessage(ClientKexManager.java:123)
	at ch.ethz.ssh2.transport.TransportManager.receiveLoop(TransportManager.java:572)
	at ch.ethz.ssh2.transport.TransportManager$1.run(TransportManager.java:261)
	at java.base/java.lang.Thread.run(Thread.java:833)

Solution:
In Redhat Linux 9 (RHEL) SHA1 has been depricated. As a work around this DEFAULT:SHA1 crypto policy can be set forcefully by executing the command : "update-crypto-policies --set DEFAULT:SHA1" .
By setting a crypto policy of DEFAULT:SHA1 to re-enable SHA-1 security will be lower down but as temporarily solution it may be used.

1. Apply the SHA1 subpolicy to the DEFAULT cryptographic policy:
command : update-crypto-policies --set DEFAULT:SHA1

2. Reboot the system:
command : reboot
Screenshot is given below:

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