My laptop is running a local neo4j server. I can use it with localhost:7474 but when i try connecting it with 192.168.1.12:7474 it is unreacheable.
Turns out linux is blocking connections other than web server port 80. Because i can access my Apache server on 192.168.1.12/
I am trying to allow TCP connections on port 7474 by using
iptables -A TCP -p tcp --dport 7474 -j ACCEPT
but it gives a response as -
iptables: No chain/target/match by that name.
How can i make other clients access neo4j server running at my laptop on port 7474. My laptop IP addr is 192.168.1.12.
I doubt that it is blocking it. Probably your neo4j server is only running at 127.0.0.1. You can check this out with netstat -nplt: you will probably see something (the apache) listening on 0.0.0.0:80 or :::80 (e.g. catchall address) but on port 7474 you will probably only see 127.0.0.1:7474 or ::1:7474. If this is the case you need to reconfigure your neo4j server to listen not only on localhost (don't know how, checkout the documentation).
Okay. I had uncommented the webserver address line but it still wasn't working.
So i reinstalled neo4j. That solved it. Weird but worked.
Related
I have shut down iptables for my server, inspite of that when I check on http://www.yougetsignal.com/tools/open-ports/ it says my ports are not open.
Where do I have to specify to open ports. I am running a linux server
Is your server/PC behind a NAT router? If so, you may need to port forward the required ports to your server/PC. A helpful website for guides on how to do so (as it depends on your router model) is http://portforward.com/
If your server is not behind a NAT router or if you've verified you're port forwarding, is the application that's supposed to be listening on the specific port even running? Try this:
netstat -anp | grep <port number>
Netstat manual page: http://linux.die.net/man/8/netstat
If you can't find the port as listening on netstat, make sure that the application is running.
You need a server program (daemon) running on a machine listening on a port for that port to be open.
Setup the 'nmap' package on your server with 'yum install nmap -y' and check listening ports on your server:
nmap localhost
If you can see your port listening then you need to check your router for proper port forwarding, else you need to make sure that your application is working and listening for the port.
For the example, Apache2 will listen for port 80 by default.
I am currently trying to open port 8787 for rstudio server. I have set this up on an ubuntu host, and want to point my browser at the ip address of the ubuntu host, using port 8787 to direct it to rstudio. I can do this from the host machine, but no such luck using a different computer.
When I do
netstat - peantl | grep ":8787"
I get nothing returned, unlike when checking port 22 which is confirmed as listening. I can there ssh from external machines into the ubuntu host.
So I tried to open up port 8787 with iptables:
sudo iptables -A INPUT -p tcp --dport 8787 -j ACCEPT
command runs fine, but then re-checking with netstat I still do not get any output (I was expecting similar output to port 22 as mentioned previously)
I also allowed port 8787 on ufw:
sudo ufw allow 8787
using gufw it confirms port 8787 is open.
What could be the issue? If my network has restricted port 8787 how can I tell? Am I allowing port 8787 correctly with iptables?
Thanks.
All your iptables and ufw commands are doing is opening ports in the firewall itself. The fact that there is no output from the netstat|grep line means that the rstudio software does not actually have the port open for anyone to connect to. This is the issue you need to fix first.
For testing purposes I want to build a server that listens for TCP connections to every port (or at least on most of the ports) on a certain interface (e.g., eth0). The server is accessed via SSH to eth1, so no problem there. (I do not care about UDP or other protocols)
I want to do a special kind of middlebox detection/analysis, therefore I need to be able to fully establish a connection. Having an HTTP connection would be the best, because the "client" could be implemented as JS in the Browser.
I started with a simple jetty server, but had to realize that jetty needs to spawn at least on thread per port it is listening to. This leads to problems when I want to listen to several thousand ports. Or is there a way around that?
My next try was to use iptables:
sudo iptables -t nat -A PREROUTING -i eth0 -p tcp -j DNAT --to-destination 127.0.0.1:8080`
It seemed to work. It allows to connect on every port and the traffic gets routed to the local port 8080 where jetty listens. But now I no longer know which port was used by the client. Because jetty thinks the connection was established via port 8080. Is there a way to determine the real incomming port from jetty? I could send the port as part of the HTTP request, but if the client tries to contact port 1234 .. and a middlebox redirects this to port 5678 .. I am unable to know what port was used.
I also tried userland solutions like socat. The problem was even worse than before. Because now jetty also saw the remote IP as being 127.0.0.1.
Or, is there another way to achieve this?
Oh and btw: I have full control of the machine. So I could change the kernel or whatever is needed. Right now I use Ubuntu 14.04 LTS, but if a solution needs something else I could go with that.
NB: This is a Python solution, because I know Python, but you can accomplish the same thing in any language the exposes the underlying C library getsockopt call.
If you replace your DNAT rule with a REDIRECT rule, you can then
use getsockopt with the SO_ORIGINAL_DST option to retrieve the
original address of a REDIRECT-ed connection.
Consider the following code:
#!/usr/bin/python
import socket
import struct
SO_ORIGINAL_DST = 80
s = socket.socket()
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind(('0.0.0.0', 2000))
s.listen(10)
while True:
csock, caddr = s.accept()
orig_dst = csock.getsockopt(socket.SOL_IP, SO_ORIGINAL_DST, 16)
orig_port = struct.unpack('>H', orig_dst[2:4])
orig_addr = socket.inet_ntoa(orig_dst[4:8])
print 'connection from', caddr
print 'connection to', (orig_addr, orig_port)
print
If I have an iptables rule that looks like:
# iptables -t nat -A PREROUTING -p tcp --dport 1500:1600 \
-j REDIRECT --to-port 2000
And while the above Python code is running I connect from another
host to my_ip_address:1500, I see:
connection from ('192.168.1.20', 35790)
connection to ('192.168.1.75', (1500,))
And if I connect to port 1550 I see:
connection from ('192.168.1.20', 42054)
connection to ('192.168.1.75', (1550,))
Which I think is exactly what you were asking for. Note that to my knowledge this will only work for TCP connections; there are other solutions (possibly involving the TPROXY iptables target) that may work with UDP connections as well.
Sorry in advance for such a noob question, but I'm certainly a noob.
My question is what does it mean to LISTEN or ACCEPT on a port as it relates to my example?
EXAMPLE:
I have a tomcat server, and It will use port 8080. I want to make sure that port is available for me to use.
What commands should I perform on my unix server and why?
what information would a command like this give me: netstat -an | grep LISTEN
If a port shows up as LISTEN in netstat, it means the port is in use by a server process, so you can't use it. Here is an example:
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN
which shows that port 631 is in use.
Ignore the UNIX type sockets at the end - they are irrelevant.
For checking port 8080 is in use or not, you can simply use the command netstat -an|grep 8080. If you get an output in below format, that means 8080 is already in use and you need to assign a new port for the tomcat.
# netstat -an
tcp 0 0 127.0.0.1:8080 0.0.0.0:* LISTEN
Netstat command displays various network related information such as network connections, routing tables, interface statistics, masquerade connections, multicast memberships etc,
a option with netstat will give you both listening and non listening ports
n option when you don’t want the name of the host, port or user to be displayed, use netstat -n option. This will display in numbers, instead of resolving the host name, port name, user name. This also speeds up the output, as netstat is not performing any look-up.
For more understand the use of netstat command here are its options:
-a : All ports
-t : Ports TCP
-u : Ports UDP
-l : Listening ports
-n : IP address without domain name resolution
-p : Name of the program and it associated PID
So:
-To display all port (TCP & UDP), PId with the associated name of the program :
$ netstat -paunt
-To display all Listening ports (TCP), PId with the associated name of the program : (and we can also filter with the grep command)
$ sudo netstat -plnt | grep ':80'
I hope it will be helpful :)
You can also use telnet to check if the port is open and listening e.g,
Zeeshan$ telnet google.com 80
Trying 173.194.35.5...
Connected to google.com.
Escape character is '^]'.
I am telnetting google.com on port 80. If you see the third line in the output, you will notice it says it is connected with the Google's web server. The same way you have a JAVA application server called Tomcat and it is listening on port 8080. In fact it is asking clients to connect to it on port 8080 so it can give away the JAVA services to client. When I will use from a client side telnet localhost 8080 I will be connected the same way I have connected with Google's web server on port 80. Provided that Tomcat is running and listening on port 8080. If port 8080 is not free and occupied by some other application you can simply change the port 8080 to another free port. Telnet should give you the following status:
accepted (connected), refused, and timeout
connection refused - nothing is running on that port
accepted - some application is running on the port
timeout - a firewall is blocking access
So now there are two possible ways to check. From the same machine you are running Tomcat server:
telnet localhost 8080
Of if you want to check it from some other machine or outside of the network:
telnet 192.168.1.1 8080
I hope that helps.
use can also run the below command, it will list the Port and corresponding PID, if any process is using those ports
netstat -tulpn
I have started the Cassandra server, before that I have changed "rpc_address" in cassandra.yaml.I can access the cassandra from the same machine but I could not access the cassandra from remote machine through Java application using Hector Client. Please help me, Thanks in advance.
I could ping the machine. But I could not access the machine using telnet in windows. The servers is linux machine. Do you have any idea ?
Your firewall is blocking off the telnet port and probably the rest of the ports cassandra needs. You need to add an exception telling the firewall to open port 9160 (the client port). 9160 is the only port you really need to have open unless you want remote jmx management etc.
To add an exception to your linux firewall:
iptables -I INPUT -p tcp --dport 9160 --syn -j ACCEPT
And if you want to save the state:
service iptables save