I need to establish a Socket connection (TCP) between two hosts (say host1 and host2) in Java. But looks like I can't do that because of a firewall. Though there's a third host (say host3) which is accessible from both host1 and host2 and I think can be used as an intermediate for this connection.
So basically, I want to send a request from host1 (client) to host3, which redirects my request to host2 (server).
Could you please let me know how can this be achieved?
Thanks in advance!
You could establish a SSH tunnel with
ssh host3 -L4321:host2:6523
and then connect from host1 to host3 on port 4321. This effectively gets redirected to port 6523 on host2.
A similiar option could be to have ssh provide a SOCKS server.
ssh host3 -D 6543
and then use curl instead of wget.
Then you can do
curl http://host2/foo/bar --socks4 localhost:6543
(untested, --socks4a and --socks5 could be an option as well...)
This ssh command creates a SOCKS server locally which tunnels the connection attempts to the ssh server, which in turn executes them.
Related
Im doing a challenge (CTF style) and everyting we got is an IP.
Scanning that IP only one port is open.
If I connect to that IP and port using netcat, I got a kind of "dance" doing in CMD, with a message at the end that says "Check socket 12345".
I need to understand again what truly a socket is because im not getting anywhere trying to connect to that socket.
Its possible to connect to a socket from a specific port? or I only can make a connection from a open port and there the web servers redirect my connection automatically to a socket?
You can use netcat nc and its -p option to set the source port.
Netcat man page say:
-p port
local port number (port numbers can be individual or ranges: lo-hi [inclusive])
Try "nc -p 12345 dest_IP dest_port"
I have a PgAdmin server running on localhost and I'm trying to connect to it from another computer on the same network (they have the same IPv4 address).
I've gone through a lot of questions but all of them explain how to connect to a remote server, which I assume is running on an available host.
I've tried:
adding listen_addresses = '*' to postgresql.conf (on both computers)
adding host all all 0.0.0.0/0 md5 to pg_hba.conf (on both computers, replacing 0.0.0.0/0 with a variety of ip addresses)
some other things I saw in tutorials but don't remember
What I'm trying to understand is:
Is it possible to connect remotely to a server running on localhost?
If it is possible, which IP address does the remote computer need to connect?
You need to resolve some basic questions first:
What is the IP of the computer where PG is running? e.g. 192.168.100.10
Which port is PG exposed on? e.g. 9999
After you collected the two above information you can go on the second computer where you have pgAmin and execute
telnet <host> <port>
substituting <host> and <port> with the info collected above. If telnet replies with
Trying ::1...
Connected to <host>.
Escape character is '^]'.
this should mean that the port is open and PG should be listening on that host:port. You found your connection string to PG!
I am just sharing my understanding here. Corrections are welcome.
pgAdmin can connect to one/more postgres servers via TCP over using JDBC like protocol. pgAdmin is just a stand-alone web-interface ( web adapter ).
So some web-server configuration/tuning should be needed in pgAdmin configuration to enable access from remote machines.
I have started an ubuntu instance on AWS EC2
e.g. [ec2-user#ip-XXX-XX-XX-XX ~]$
Inside this instance, I am running a socket program for sending the data to my local system.
The program is running properly, but not able to connect to my local IP.
I am trying to ping my local system also from AWS ec2 user, but it is also not working.But I am able to ping google(8.8.8.8).
e.g. [ec2-user#ip-xxx-xx-xx-xx ~]$ ping xxx.xxx.xx.xx(my local IP)
I have set all security groups(inbound), like All Trafic,All TCP and so on.
Sorry for bad English.
Thank You
Your computer (PC) cannot be pinged from an AWS hosted machine
This is probably because the VM on your computer is using NAT outbound to talk to the LAN, which goes to an Internet router, which sends the packets to AWS
The reverse route (inbound to your PC) does not exist so starting a ping echo request from a AWS machine will not work
It is possible to get around this by opening a pass through on your router but generally this is not a great idea
However if you want to make a socket connection securely there is a way
First, start a ssh session with remote port forwarding. In the Linux ssh client this is using the -R option.
For example, if your local system is running a listening service on port 80 and your remote system has the address of 54.10.10.10 then
ssh -R 8080:localhost:80 ec2-user#54.10.10.10
Will establish a circuit such that connections to the "localhost" on the remote ec2 server on port 8080 are connected to the "localhost" on port 80 of your local machine
If you are not using a ssh cli program, most ssh clients have a facility of this sort.
Note that it is necessary to keep the ssh session open to be able to use the connections
I have a socket that listen on port 6100 on my development machine, whose lan address is 192.168.1.2
I can access the socket and use it with the address 127.0.0.1:6100, but I can't access it from 192.168.1.2:6100 (I need to access the socket from another client on the Lan)
If I type netstat -an | find "6100" on the command prompt I get:
TCP 127.0.0.1:6100 0.0.0.0:0 LISTENING
So I need to redirect all calls to 192.168.1.2:A_RANDOM_PORT to 127.0.0.1:6100
How can i do that?
I tried with:
netsh interface portproxy add v4tov4 listenport=6200 listenaddress=192.168.1.2 connectport=6100 connectaddress=127.0.0.1
But without luck
I've finally been able to accomplish this task, but only using an external tool.
I downloaded "PassPort port forwarding utility" and set up a redirection from 192.168.1.2 to 127.0.0.1
Unfortunately I haven't been able to do that without an external tool.
You failed to post the code concerned, but you bound your listening socket to 127.0.0.1 instead of 0.0.0.0. Just fix that. No oort forwarding required.
Is there a dedicated port (lower than 1024) specifically for clients to send text based console output to a server? I've googled extensively but to no avail. What's the best port (lower than 1024) for sending text based console output if any?
A port is just a number. You can see well known port assignments in /etc/services.
You need a server application to be listening on the given port to accept your input. There are number of remote terminal protocols and their implementations, among which are Telnet (port 23) and Secure Shell, or SSH (port 22).
The simplest way to test your socket client is to setup netcat on the server to listen on whatever port you want (port is 777 in the example bellow), and then try to connect to it from somewhere else:
server:~# nc -l -p 777
then
client:~$ nc server 777
Note that on Unix you normally need super-user (root) rights to bind "privileged", i.e. bellow 1024, ports.
I'm going to use telnet (port 23) since that's closest to what I want. Sending console messages to a server from a client. okey dokey thanks!