Can't create sockets to domain - sockets

I'm running ubuntu 10.04 lts on my server.
I ran into a problem where my server.jar file couldn't create an SSL socket to prod.euw1.lol.riotgames.com.
I tried "telnet prod.euw1.lol.riotgames.com 2099", but it can't establish a connection.
However, "telnet prod.euw1.lol.riotgames.com 2099" runs fine on a different ubuntu 12.xx server that I ssh'd into, and it works fine on my personal computer.
And strangely, connections to other host servers with "telnet prod.na1.lol.riotgames.com 2099" or "telnet prod.eun1.lol.riotgames.com 2099" on my ubuntu 10.04 machine work just fine.
I don't know what steps to take next, I've already flushed my iptables rules to accept all incoming/outgoing traffic, and the IP address that the domain resolves to is the same across all of the computers I've tried.

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Memcached: cannot connect to server with libmemcached but telnet works

I have a program that is using libmemcached client in c. When working with localhost (server on same machine than client) everything works fine. When trying to run the server and client on different machines, the client cannot connect to it. I get the error message: "SERVER HAS FAILED AND IS DISABLED UNTIL TIMED RETRY".
However, when connecting through telnet (telnet ip port) the client machine can connect to the server (even when they are not the same machine). Both machines are on the same network so I am using interface eth0. Pinging works fine.

Having problem in connecting to remote MongoDB Server

I tried to connect a remote MongoDB Server running on Ubuntu using MongoDB Compass on Windows. But I have problems connecting always as the IP of the Windows machine changes every day.
I did the following things to connect to the remote server-
Got the IP of the Client Machine, then allowed that IP on the firewall of the server machine on port 27017.
sudo ufw allow from client_machine_ip to any port 27017
Note: The ufw status looked okay.
Got the IP of the Server Machine, then on the MongoDB configuration file on the server, I modified the bindIp.
bindIp: 127.0.0.1,server_machine_ip
Note: I restarted mongod and it was okay too.
I was able to connect the remote MongoDB Server using MongoDB Compass successfully for the first time. Then I saw, the IP of the client machine was changing every day. So, every time, the client IP changes, I need to allow that IP on the firewall of the server machine (in which I am using the MongoDB Server) on port 27017. Could you help to solve this? Thanks in advance.
You can update the firewall for port 27017 to allow from anywhere since client machine IP is not static.
sudo ufw allow 27017 #(this will allow from any IP)

vsftpd installation on ubuntu 16.04 LTS

I'm use Linux server with vsftpd connection created successfully but i can't retrieve the files
Your screenshot shows that the connection timed out when trying to transfer something (LIST) after switching to Passive Mode (PASV). In my opinion, probably your firewall is not correctly configured for Passive Mode and therefore is blocking the connection.
Try allowing incoming (inbound) connections on port 40000 to 50000 for all IP address or the IP address of your FTP client. Configuring firewall is firewall-specific, therefore, I cannot give you detailed instruction on how to do this.
sudo ufw allow 40000:50000/tcp
sudo service vsftpd restart

How to ping to my local machine from AWS EC2 instance?

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

PostgreSQL SSH port forwarding via Windows/PuTTY

I have PostgreSQL 9.4 running on a Linux VPS, and I need to be able to connect to it over SSH from both Linux and Windows clients. (I will later need to connect to multiple servers, and so that all clients use the same port numbers, I'm forwarding to port 5551 for the first server, then I will use 5552, 5553, etc.)
From a Linux client I just run ssh -fNg -L 5551:localhost:5432 user#remote1.com and connect to localhost:5551 with PGAdmin3 or any other client app. Works great.
On Windows, I'm using PuTTY and Pageant. I got the connection to user#remote1.com via terminal working, then I went to the SSH Tunnels and added L5432 localhost:5551. Terminal connection still works, but when I try to connect with PGAdmin3 to localhost:5551 I get an error:
could not connect to server: Connection refused (0x0000274AD/10061) Is the server running on host "localhost" (::1) and accepting TCP/IP connections on port 5551?
I resolved it. Like many things, this is obvious in hindsight. I had things backward in the SSH Tunnels setup in PuTTY. It needs to be L5551 remote1.com:5432