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can't connect to mqtt broker via ssl

I have a raspberry running a mqtt broker and a java backend. I can't establish a connection from backend to broker since I've implemented ssl. I can connect the backend to the broker on raspberry from my IDE running on my MacBook like:
client = new MqttAsyncClient(
"ssl://my-domain.com:1883", "backend");
if the backend is on the raspberry I tried:
client = new MqttAsyncClient(
"ssl://localhost:1883", "backend");
client = new MqttAsyncClient(
"ssl://127.0.0.1:1883", "backend");
No success. I´ve never used a ssl connection in this context. did I oversee something?
Error:
Exception in thread "main" No connection to client (32104)
at org.eclipse.paho.client.mqttv3.internal.ExceptionHelper.createMqttException(ExceptionHelper.java:31)
at org.eclipse.paho.client.mqttv3.internal.ClientComms.sendNoWait(ClientComms.java:143)
at org.eclipse.paho.client.mqttv3.MqttAsyncClient.subscribe(MqttAsyncClient.java:721)
at org.eclipse.paho.client.mqttv3.MqttAsyncClient.subscribe(MqttAsyncClient.java:681)
at com.cdh.Service.mqttManager.subscribe(mqttManager.java:243)
at com.cdh.main.main(main.java:14)
EDIT:
I changed the port to 8883. It works if I run the backend on an other device but not if the broker and the backend are on the raspberry. I also tried to use the domain name from my cert.

The hostname you use to connect needs to match the CN or SAN entries in the certificate presented by the broker or else it will fail validation.
Unless you included 127.0.0.1 or localhost in the certificate the the client will reject the connection because the certificate doesn't validate for that address.
p.s. you should probably use a different port for MQTT of TLS rather than 1883 as that is the standard port for MQTT without TLS.

SSLHandshakeException when trying to connect to host

I am using the weblogicserver and I have enabled HTTPS connector.
I have a standalone Java program which connects to a site say, "xyz.com" and fetches me json over HTTPS. But when I try to run the same program on the server, it throws SSLHandshakeException.

Post the stacktrace...Have you added the certificate into weblogic trust store "cacerts"?
What are your java_options settings?If not set then try something similar to below
JAVA_OPTIONS="-Dweblogic.security.SSL.trustedCAKeyStore=/weblogic92/server/lib/c‌​acerts ${JAVA_OPTIONS}"

Missing ServerHelloDone while SSL Hanshake

I try to connect to a wss (Secure Websocket) server with a java applet but the ssl handshake fails without any helpfull log entrys.
If I connect to wss://echo.websocket.org the handshake works fine, so I think it's not a general java code error.
If I try to connect to my own server, the HelloDone bit is sent (verified by wireshark) but the connections ends in a hang-up and it's not in the log. Normally there should be the following message in the log: "*** ServerHelloDone"
See my java console log of "javax.net.debug=sll"
http://pastebin.com/ZuvKww4J
It is not truncated, it simply ends there.
After a couple of seconds the tcp connection timeout message is added to the log.
I use the following example of java code:
https://github.com/TooTallNate/Java-WebSocket/blob/master/src/main/example/SSLClientExample.java
But instead of keystore I use:
sslContext.init( null, null, null );
For the server I have two different test systems:
At port 443 a ha-proxy
at port 8443 a stunnel.
I tried to isolate the error with different methods. First I forced with stunnel the same cipher as echo.websocket.org "SSL_RSA_WITH_RC4_128_SHA" but no success.
Second I checked if the ssl certificate itself is still valid. But as web browser and normal https connection by my java applet, are accepted from the server (Same server. ha-proxy orstunnel) everything is working at that point to.

Problem was solved by maintainer of Java-WebSocket.
Big thans

Connect to FTPS through proxy

The initial problem we encountered was that a regular FTPs download started failing due to an untrusted server certificate. This prompted us to wonder whether the certificate had been updated without the counterparty notifying us so we wanted to download the current certificate and compare it to the one we have in our keystore.
This seems to be a trickier problem than we had anticipated. The usual suspects (firefox, filezilla, ...) did not seem up to the task of connecting to an FTPs server through an FTP proxy so out of curiosity I started playing around with a more low level java approach. I can not for the life of me get it to work though.
First (overly simplistic) java attempt:
// create proxy connection
SocketFactory plainFactory = SocketFactory.getDefault();
Socket proxy = plainFactory.createSocket(proxyServer, proxyPort);
// create ssl connection on top of it?
SSLSocketFactory sslFactory = getSocketFactory();
SSLSocket socket = (SSLSocket) sslFactory.createSocket(proxy, server, port, true);
This approach obviously does not work.
Next I started playing around with ftp4j (http://www.sauronsoftware.it/projects/ftp4j/) it seems to have a clean and accessible codebase:
FTPClient client = new FTPClient();
client.setConnector(new FTPProxyConnector(proxyHost, proxyPort));
client.getConnector().setConnectionTimeout(0);
client.getConnector().setReadTimeout(0);
client.setSSLSocketFactory(getSocketFactory());
// also tried SECURITY_FTPS
client.setSecurity(FTPClient.SECURITY_FTPES);
client.connect(server, port);
This outputs:
REPLY: 220 Blue Coat FTP Service
SEND: USER anonymous
REPLY: 530-User Access denied.
REPLY: 530-
REPLY: 530-Usage: USER username#hostname
REPLY: 331 PASS userpassword
Exception in thread "main" java.io.IOException: Invalid proxy response
The proxy server has optional authentication and on our development servers we generally use "user#host" without proxy authentication. As such I assume the username, hostname and password are those of the remote server?
So I tried adding the remote parameters, this does not work:
REPLY: 220 Blue Coat FTP Service
SEND: USER test#ftps.example.com
Exception in thread "main" java.io.IOException: FTPConnection closed
Adding the proxy user to match the bluecoat format does not seem to work either:
USER %u#%h %s
PASS %p
ACCT %w
Any help with either of these two problems would be most welcome:
how to retrieve the server certificate from an ftps server through an ftp proxy
how to connect to an ftps server through an ftp proxy in java

You might want to try Apache Net commons libs.
Here is a similar thread that uses that Net Commons library
Net commons also has a fully functional FTP Client Example so you can test with something you know works.

could not open connection to the host, on port 23: Connect failed

I have extremely simple chat server (100 lines of code on Java) and it is working properly. When I'm testing it with Telnet on localhost everything is just fine. When I asked some of my friends to test it with telnet (telnet <myIP> <port>, the port I assigned is 5555, server is running on my PC with static IP) everything is just fine too, but one of my friends received the error
Could not open connection to the host, on port 23: Connect failed
when he was trying to connect. Every firewall, anti-virus and anti-spyware software is turned off from both sides. Why could some of my friends connect but not him? Where is the problem: is it on the server or his PC?

I had a similar issue before and what it turns out to be is the syntax. When I do:
telnet 192.168.10.10:3333
I will get the port 23 error but if I type in:
telnet 192.168.10.10 3333
I will get correct result.

Try to make the telnet connection as
telnet 192.168.10.10 3333
without using :

Your friend's Telnet client is obviously attempting to connect to port 23, not 5555 or 43839, since that's what it says in the error message he is getting.
Ask your friend to check the documentation for the Telnet client he's using, and make sure he's specifying the port the proper way.