telnet-echo-server | Simple telnet | Telnet library

I was able to figure out solution for above issue. Basically I executed below steps.

1. First I started vault server in above machine ( '123.456.XXX.X' ) by below command

By default, AWS blocks outbound traffic on port 25, and you have to file a request to get the restriction removed.

I usually just use a different SMTP port instead of trying to get port 25 opened. SendGrid's documentation states:

SendGrid accepts unencrypted and TLS connections on ports 25, 587, & 2525. You can also connect via SSL on port 465. Many hosting providers and ISPs block port 25 as a default practice. If your Telent session continually times out or will not connect using port 25, it is likely that your ISP or hosting provider is blocking the port. You can contact your host/ISP to find out which ports are open for outgoing SMTP relay. We recommend using port 587 to avoid any rate limiting that your server host may apply.

I suggest just switching to use port 587

The Connection timed out message normally indicates that there is no network connectivity.

In most cases, this is due to the Security Group.

The steps to check it are:

• Select the instance in the Amazon EC2 management console
• Go to the Security tab
• Check the Inbound rules

To permit an SSH connection, there needs to be a rule that permits port 22 (SSH) and the source set to your IP address or from the whole Internet (0.0.0.0/0) -- preferably only your IP address so that everybody else will be blocked.

When launching an Amazon EC2 instance from the console, it will default to creating a new Security Group called launch-wizard. However, it is generally better to create your own Security Group with a useful name and only the rules you want. You can then re-use that Security Group in future for similar instances.

The server doesn't send a newline, but the client is waiting for it. It works with telnet because telnet prints characters as they arrive without waiting for a full line.

as far as kunif just commented my post (thank you again) I would like to share the info as an answer to make everybody has my problem, able to fix it properly.

Following this link you'll get instruction that make you able to spawn a virtual COM to connect to an APP can be link to a generic serial over ethernet.

WINDOWS - ComPort over Network

This works fine with me. Hope it works with you too.

PS. instruction would introduce you to both Windows or Linux approach to the issue.

Ale_Trex

Oh now I've got it, 'echolog' is your function, I though it's some app at first sought. It could be simplified like this:

I guess the idea behind this question is that if you're looking at a webpage you can do "view source" in the browser and look at the HTML, CSS, and Javascript that make up that page.

Of course, what you're seeing there is just the "client side" part of the web page. You can't click "view source" on Facebook and see the code that accesses their database, decides what to show in your feed, picks out the ads you're going see, etc., because that's all done server-side. Nor can you see the source code for the web server that handles your incoming connection, etc.

In the case of a telnet server, the "client side" portion is just the raw text you're seeing. There's nothing [1] analogous to what you'd see if you did "view source" in a browser beyond what you're already seeing in your telnet window.

Of course, if the program that they're running on the server side is publicly available, you may be able to download and read its source code. This is analogous to how, if a web site is running on apache or nginx, you can just download the source code for those and read them. But this is not something that's sent over the telnet connection.

[1] Slight nitpick: I guess technically if the text you're seeing has VT100 control sequences to highlight or colorize the text that is sort of analogous to HTML code, but it's very limited. If that's what you want to know about, you could either set your telnet client not to process those sequences in order to see what they look like, or you could capture the network traffic with something like tcpdump. But you can also just look up VT100 control sequences.

I debugged your example and in my case, I needed to wait for the program, which you connect via telnet, until it is ready to receive a command.

In the second step, you can send your command and the exit command to stop the telnet, so you are reading from the stream until it has stopped by saying "Connection closed...". Be aware, that exiting from telnet can have different commands, some use quit, some other use exit or only wait for a termination signal.

You create connection to only one switch