I have a server, to which a client machine connects. Recently I decided to encrypt the connection with stunnel, so now client program connects not directly to the server, but to localhost:8045 (I checked, and this port is not occupied).
Java code:
URL url = new URL("http://localhost:8045/malibu/GetProviders");
InputStream stream = url.openStream();
And I get the following:
java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:519)
at java.net.Socket.connect(Socket.java:469)
at java.net.Socket.<init>(Socket.java:366)
at java.net.Socket.<init>(Socket.java:180)
. . .
If I try to request the same page using curl, everything is fine.
What can cause such behavior?
EDIT: Yes, there is a listening socket - running netstat -avn | grep 8045 gives:
tcp6 0 0 ::1:8045 :::* LISTEN
The listening socket is bound to the IPv6 loopback address (::1). I recall some issues with Java not supporting dual-stack IPv4/IPv6 systems correctly; this is probably such a case. It is connecting to 127.0.0.1 only (IPv4).
Everything else you have tried (curl, telnet...) will try the IPv6 address first, and then fall back on the IPv4 address if that fails. That's why they work, while the Java application does not.
Try forcing stunnel to bind to 127.0.0.1. You might also try having Java connect to http://[::1]:8045/malibu/GetProviders, though I can't recall if it supports IPv6 addresses in HTTP URLs.
I have Apache on Windows and also connection refused from Java. However debugging the connection and the Apache log shows, that it is actually not a connection problem. Apache returns error 301, permanently moved. Then it provides a redirection url to non-existing port 8080. So something's wrong with the server configuration, probably ServerName directive uses wrong port. Adding a trailing slash to the requested url fixes the problem. The most useful debugging output in my case was given by wget.
It's possible that the accepted answer does not explain the phenomenon. The reporter himself admitted in a comment that finally he used a url with slash at the end.
Related
Launch error: Failed to connect to remote VM. Connection timed out
Project -SDK
Connection type - Standard (Socket Attach)
Host: IP address of the SAP server
Port: 8080
There is nowhere like enough information in your question to identify the actual cause of your problem (or the fix), but problems like this typically occur because:
you are using the wrong hostname or IP address when connecting to the server
the server is off
a firewall is blocking your access to the server
there is something wrong with the network.
Hope this will give you some ideas about what to look for.
I'm trying to use JavaMail in order to connect to an IMAP Server (on a remote virtual linux machine - Ubuntu 14 LTS) but I'm getting the following exception:
java.net.ConnectException: Connection refused
I've already tried to establish the connection via Telnet and everything works.
The JavaMail version I'm using is 1.5.5 (also tested with 1.4.7) and I'm using the following properties:
Properties properties = System.getProperties();
properties.setProperty("mail.imap.host", SERVER);
properties.setProperty("mail.store.protocol", "imap");
properties.put("mail.imap.port", PORT);
Session session = Session.getInstance(properties, null);
Store store = session.getStore("imap");
store.connect(USERNAME, PASSWORD);
Notes:
It's working on my personal machine
It's working on another external machine
It's failing on the remote linux virtual machine
The IMAP server is on a different machine - which is accessible to all of the previous
I've done some research and some people told that it could be a firewall/blocking issue but how am I able to connect via Telnet?
Thanks.
Edited
The telnet command I've applied in the test-run:
telnet <server_ip> <port>
After this, the connection is successfuly established and I'm able to apply IMAP commands such as list status.
The output from javamail when it fails is the following:
java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:529)
at java.net.Socket.connect(Socket.java:478)
at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:233)
at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:189)
at com.sun.mail.iap.Protocol.<init>(Protocol.java:107)
at com.sun.mail.imap.protocol.IMAPProtocol.<init>(IMAPProtocol.java:104)
at com.sun.mail.imap.IMAPStore.protocolConnect(IMAPStore.java:538)
... 12 more
Firewalls usually work port based. This means telnet (23/TCP) can be allowed whereas IMAP (usually 143/993) is blocked.
You should check the firewall and check if the IMAP port is open.
Where is your program running? If you change getDefaultInstance to getInstance does it work?
I've found a solution!!
I performed a network capture on the remote machine and I saw that for some reason the javamail api was using the default IMAP folder and not the one I've selected..
Further tests revealed that changing the property value type to String instead of Integer solved this issue. It's important to notice that this didn't happen on other environments so I'm not sure the reason I had to make this change.
I can SSH and PING a machine running Fedora 18, but whenever I try connect to it using Sockets, I get NoRouteToHostException (I tried Java and C++, and I get the same error).
Any ideas? I have looked around but could not find a solution that works.
If you're not trying to connect to the same port that ssh(1) uses (port 22) then the problem could be that a firewall exists between you and the destination and it doesn't allow your packets through. You can test this by having your code try to connect to port 22 on the destination host. If you don't get the same exception, then this is the likely cause.
You should also verify that your code is OK by having it try to connect to the local host (i.e., the computer on which it's running). You should not get the no-route-to-host exception (unless the firewall on the local host is doing something odd)
I am getting
Caused by: java.net.NoRouteToHostException: No route to host
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:529)
at com.sun.net.ssl.internal.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:564)
at sun.reflect.GeneratedMethodAccessor638.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.commons.httpclient.protocol.ReflectionSocketFactory.createSocket(ReflectionSocketFactory.java:140)
at org.apache.commons.httpclient.protocol.SSLProtocolSocketFactory.createSocket(SSLProtocolSocketFactory.java:130)
at org.apache.commons.httpclient.HttpConnection.open(HttpConnection.java:707)
at org.apache.commons.httpclient.HttpMethodDirector.executeWithRetry(HttpMethodDirector.java:387)
at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:171)
at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:397)
at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:323)
javadoc says
Signals that an error occurred while attempting to connect a socket to
a remote address and port. Typically, the remote host cannot be
reached because of an intervening firewall, or if an intermediate
router is down.
Is this error on client side or remote side or it can be either of these?
Basically it says that your client cannot connect to the server due to the address is inaccessible from the client machine.
Please check that the address you are connecting to is accessible, either via ping command in your Command Prompt (Windows) or terminal (Unix-based):
ping <address>
or if it's a web server you can try to check it in your web browser.
The ping command is helpful for me in most cases, since I would know why exactly I can't connect to the address. It can be a mistyped address or like the javadoc suggests, problem with firewall.
Either. It could be a firewall on the client machine blocking outgoing calls or somewhere at the other end.
It may be possible the ping will provide responses, but the application may still fail to connect.
If that is the case, I would suggest using telnet to try and connect to the host using the desired port, telnet host.address port
If the connection is refused then the port on the host will need to be allowed. It that succeeds, but the application still won't connect:
Verify the address:port being used in your application are the same as those used in the telnet test.
It may be a local port on the client blocking the connection, in which case you would need to allow the port on the client
In my case it was solved like this:
1 - Clear the cache with 'yarn cache clean' or 'npm cache clean --force'
2 - after that reboot the pc.
If you clear the cache but do not reboot, the data will still be stored 'somewhere' on the network, so the port will not connect, it is still busy.
After restarting it connects smoothly.
I hope I was helpful!
I had the same issue, and resolve it by disabling the firewall on both sides :
systemctl disable firewalld
service firewalld stop
I had the same issue, I did run iptables flush on host server, this fixed the issue.
# iptables --flush
I have this error/exception-
SQL Exception: com.microsoft.sqlserver.jdbc.SQLServerException: The TCP/IP connection to the host localhost, port 1433 has failed. Error: "connect timed out. Verify the connection properties, check that an instance of SQL Server is running on the host and accepting TCP/IP connections at the port, and that no firewall is blocking TCP connections to the port.".
and my code is-
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
String connectionUrl = "jdbc:sqlserver://localhost:1433";
Connection con = DriverManager.getConnection(connectionUrl,"","");
System.out.println("ok");
} catch (SQLException e) {
System.out.println("SQL Exception: "+ e.toString());
}
catch (ClassNotFoundException cE) {
System.out.println("Class Not Found Exception: "+ cE.toString());
}
how can i sovle it,please help me.
This could mean almost anything - basically, it was impossible to connect to port 1433 on localhost. Could be a network problem, could be that the database is not started, could be that it is running but not bound to port 1433.
In a pinch, you can always open a shell and run
telnet localhost 1433
to see if it is possible to make a connection at all.
I had this error.
I fixed it by going into the SQL Server Configuration Manager.
Under SQL Server 2005 Configuration -> Protocols for SQLEXPRESS. Look at the IP Address tab of the Properties of the TCP/IP Protocol.
At the very bottom of the protocol list (under IPALL), the TCP Port field was blank. I put 1433 there, saved, restarted the SQL service and it worked great :)
It's telling you it can't connect.
Check that sql server is available on your local machine on that port.
Check that sql server is accepting connections with the blank name and password you're providing in your getConnection() invocation.
Check that your jdbc url is in the correct form, they're sometimes manufacturer/driver specific.
The error just means that java was not able to connect to your database. Either database is not running or your firewall is blocking connections to it. If you are sure your DB server is up on your localhost, try after disabling your windows firewall.
Lets look at some of the possibilities:
The database server is not listening on localhost:1433 : you probably would get a "connection refused" rather than a "connection timed out"
The database server is catatonic (i.e. in a state where it is not responding to requests) : you could get a "connection timed out".
The database server is massively overloaded : you could get a "connection timed out", but you would probably notice that the machine was very slow.
The local software firewall is configured to block all requests to port 1433 : you could get either "connection refused" or "connection timed out" ... or some other response. (It depends exactly what the firewall does with unwanted traffic.)
The loopback interface (for IP 127.0.0.x) is not configured : you are more likely to get "no route to host" or "no route to network".
The DNS entry for localhost is misconfigured (i.e. localhost doesn't resolve to 127.0.0.x) - lots of things could happen ... depending on how it is misconfigured.
Here are some things you could do to diagnose the problem ... depending on your system:
Look at the configured networks using ipconfig or ifconfig.
Look at "/etc/hosts" to check the entry for localhost
Try to connect to the service using telnet -p 1433
Use "ps" or the task manager to see what processes are running.
Check the local firewall configs to ensure that 1433 is open for (at least) TCP from the configured localhost IP address (probably 127.0.0.1).
I had a problem similar to this, and solved it by adding the line:
System.setProperty("java.net.preferIPv4Stack", "true");
The problem was it used IPv6 instead of IPv4 to access the db host (I used it for a DB on a remote host, not localhost).
Hope it helps.