Questions tagged [telnet]

For questions about Telnet, a protocol for bidirectional interactive text-oriented communication with remote hosts via virtual terminals. It is defined in RFC 854.

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Connection closed by foreing host - Postifx, Dovecot

2024-02-07T10:44:27.271322+00:00 ubuntuserver postfix/postfix-script[23192]: starting the Postfix mail system 2024-02-07T10:44:27.277625+00:00 ubuntuserver postfix/master[23194]: daemon started -- ...
-1 votes
1 answer
31 views

Telnet SmarterMail: 550 This is a submission only port. You must authenticate before sending mail

I have a "newer" server running Windows Server 2019 and I installed Smartermail FREE Edition so I could send mail via PHP/CDONTs from contact forms to my email address. I tried matching the ...
0 votes
1 answer
5k views

EXIM SMTP allows to send mails without login / authentication via telnet to any domain

I'm ashamed, but I have to ask for help. My server is being used for sending spam, I've found out I can simply connect with telnet (edit: from any server in office, home and even directly from CMD/...
7 votes
3 answers
14k views

Send test mail using telnet via smtps (465) port

Based on this guide I am trying to send a test email using telnet from linux https://linuxconfig.org/send-an-email-using-telnet but the connection immediately disconnects: $ telnet smtp.gmail.com 465 ...
0 votes
1 answer
250 views

connection refused mysql with telnet

i have 2 machines that can see each other and ping my issue is i want to telnet from slave machine to master machine and this is what i get: slave@slave:~$ telnet 192.168.1.131 3306 Trying 192.168.1....
11 votes
3 answers
8k views

How to quit QEMU monitor?

I launched KVM VM with this command: kvm /kvm/hdd/v1/v1-1.raw -m 512 -daemonize -smp 2 -nographic -net nic,model=virtio,macaddr=aa:aa:aa:aa:aa:01 -net tap,ifname=tap0 -monitor telnet:localhost:7001,...
0 votes
1 answer
73 views

Can't telnet Apache2 Web Server from WAN on port 80

Is there specific port configuration to httpd.conf that opens port 80 aside from using Listen 80 directive? netstat -aon gives LISTENING but I cannot telnet machineName 80 (says failed to connect) PS: ...
0 votes
0 answers
90 views

RHEL Server Accepts Telnet from all Clients Except a Rocky Linux VM

I have a few VMs on a XenServer. One is a RHEL 8.7 running SSH server. Another is a Rocky Linux 8 client and also some other Ubuntu and Windows systems. The Ubuntu and Windows systems can telnet to ...
0 votes
1 answer
115 views

How to exit from telnet in xterm (ctrl+], ctrl+'+', ctrl+d) don't work

Can't exit from telnet while connected to host. Commands like (Ctrl+], Ctrl+'+', Ctrl+D) etc. don't work. I have tried all the suggestions from keyboard shortcut to quit 'telnet'. Are there ...
1 vote
0 answers
228 views

Not receiving any response from SMTP server after successfully connected via openssl or telnet

I am trying to set up my postfix using Gmail smtp relay server. I have set it up in other servers without issues, but I am having difficulty getting it to work in my work network. I tested if there is ...
0 votes
0 answers
77 views

How do I read telnet data and save to a new log file every day?

I use to use Indigo Terminal Emulator from shadeBlue. I can't buy a license anymore, shadeBlue is not in business, and I had to migrate servers. I am using Putty to read my data and save it to a log ...
0 votes
1 answer
60 views

What is the name of the string that a service returns when you establish a tcp connection via telnet?

If you telnet to an ssh server, it will establish a connection and return a string, something like SSH-2.0-OpenSSH.... etc. Something similar happens if you connect to a mysql server. What exactly is ...
305 votes
8 answers
1.4m views

Check if port is open or closed on a Linux server?

How can I check if a port is listening on a Linux server?
1 vote
2 answers
6k views

Telnet: Unable to connect to remote host: Connection refused (Postfix - Ubuntu 14.04 VPS)

I have installed postfix following this tutorial but when I try to telnet mail.mydomain.com 110 (995,993,143 or 25) it throws the following error: Telnet: Unable to connect to remote host: Connection ...
50 votes
6 answers
128k views

How to check that an OpenVPN server is listening on a remote port without using OpenVPN client?

I need to check that an OpenVPN (UDP) server is up and accessible on a given host:port. I only have a plain Windows XP computer with no OpenVPN client (and no chance to install it) and no keys needed ...
0 votes
2 answers
2k views

Sending Email by SMTP IIS7.5 via php site

After my company decided to change the website we switched from old ASP.NET site to new website created in Drupal(php). The site is running locally on IIS7.5 and we also have virtual SMTP server on ...
0 votes
1 answer
2k views

Missing or skipped ICMP_Seq In AIX Ping

I noticed an intermittent slow response on the ping from my application server to my database server. So to diagnose, I tested using a standard ping and Telnet tests. For the telnet tests, it was ...
20 votes
3 answers
8k views

How to kill a telnet client with rlwrap since ^] does not work?

When I use telnet with rlwrap it looks like there is no way to kill the client. Am I missing something here or I really have to kill the process with the kill command?
1 vote
2 answers
3k views

"Connection failed" error when trying to telnet into SQL Server

I have an SQL Server running on a computer, and I'm trying to access it from another computer in the same local network (potentially VPN, since it's located in a datacenter). The point is that I can't ...
0 votes
0 answers
301 views

Cisco Switch - Enable Telnet using HTTP

I'm trying to automate the configuration process of a Cisco switch (SG-300). I was able to automate everything I need using telnet, but the last issue I still have is to enable telnet itself. For now ...
0 votes
1 answer
571 views

Automate time and date through telnet

im not very clued up with telnet commands but i am looking to automate logins for a device we use in the field. we are having issues with Cmos batteries and every time the power goes out (6 times a ...
1 vote
0 answers
544 views

Linux: telnet arrives to target but no response

We have server in AWS that's trying to connect over TCP to an application in an on premise server but fails. Initially we thought it might be routing/firewall issues so we tried to connect to that ...
0 votes
1 answer
2k views

How to telnet to a unix socket in debian to test memcached

To test memcached on Ubuntu, I would run this command: echo "stats settings" | nc -U /run/mydir/memcached.sock However now I have changed to Debian, and Debian nc does not support the -U ...
0 votes
1 answer
247 views

Iptables + telnet not blocking ports

I have a Debian server from which I want to block all incoming and outgoing ports (especially all outgoing email ports), except those that I specifically add in iptables. The current setup I have is ...
0 votes
0 answers
427 views

Telnet reconnect or maintain session?

We currently have several RFID Scanners connected to the backend via a telnet client. However due to coverage of our wifi these scanners might lose there connection for a small period of time. The ...
0 votes
1 answer
289 views

telnet only works one way

I recently cloned two AWS CentOS 7 instances from a physical server. From the first AWS instance, I can telnet on port 22 to the second AWS instance. From the second AWS instance, I cannot telnet to ...
0 votes
0 answers
351 views

Allowing IP & Port specific traffic for card terminal

I hope you can help me :) I am setting up a credit card terminal in my store network. (It‘s just a mobile LTE Router with a static IP address and a switch) The payment processing provider requires me ...
2 votes
1 answer
298 views

All Outbound Traffic Uses IPV6

I have a Debian 10 server which has postfix installed, each time I try to send outbound mail traffic, the server uses IPV6 over IPV4. This causes postfix to log Connection timed out. I have tried ...
1 vote
0 answers
690 views

Postfix + Dovecot and folder "sent mail"

We’re using for sending mails our own mail server Postfix + Dovecot with parameter for Postfix sender_bcc_maps which ensures that sent mail thanks to blind copy (BCC) is also sent to a sender’s ...
0 votes
1 answer
5k views

Connecting To 127.0.0.1…Could not open connection to the host, on port 8123: Connect failed

Well aware this has been asked, but I have scoured Google/StackOverflow and tried every single suggested solution, without being able to connect to port 8123 on my local (which is running Windows 10). ...
12 votes
3 answers
149k views

"-bash: telnet: command not found " error?

I have the following services running: sshd 0:off 1:off 2:on 3:on 4:on 5:on 6:off syslog 0:off 1:off 2:on 3:on 4:on 5:on 6:off tcsd 0:...
0 votes
1 answer
3k views

How to use curl and telnet instead of cgi-fcgi?

I am using this script.c: #include <fcgi_stdio.h> #include <stdlib.h> int main (void) { while (FCGI_Accept() >= 0) { printf("Status: 200 OK\r\n"); printf("Content-...
13 votes
3 answers
68k views

Contacting DNS server via command line interface [closed]

So, we are on the DNS chapter in our class, and I was wondering if there's any way possible though which I can connect to a DNS server on port 53 via command line interface (i.e Telnet or netcat) like ...
0 votes
1 answer
619 views

Telnet connects to server but cannot transmit data

Our client has a server and our web apps run on port 443 and 2000. Our client has two groups of IP addresses. One group is for the computers used in the company building. These computers can browse ...
0 votes
1 answer
252 views

Simple code running in systemd exits to fast?

I had this old code base running in xinet d. It was basically a simple python script that waited for standard in to come in on a socket, it would do something with it and respond on standard out. ...
1 vote
1 answer
4k views

Windows to Linux Ping not working while Telnet works

On Linux we have a service running which is listening on port 9999 but when we try to check it from a Windows machine on same network with PING it says : Ping request could not find host 10.32.9.82:...
2 votes
2 answers
2k views

Postfix - How to enable SMTP authentication on local delivery

I have an email server running Postfix. Everything is working fine, However, recently, some internal emails received emails from their own addresses with phishing content. After finding out, I learned ...
-1 votes
3 answers
2k views

How does one make a temporary telnet responder with PowerShell? [closed]

I'm looking into making a temporary Telnet server so I can remotely test network connectivity and data transmission integrity. I don't have the authority to install the telnet server Windows Feature.
0 votes
1 answer
309 views

How can I lock down an SSH and/or telnet user to only run a custom shell and no other commands or programs?

I asked this question on stack overflow, but I thought it might be more appropriate here on serverfault, because it has to do with system administration and security. I am looking to prototype a ...
0 votes
1 answer
602 views

telnet disabled, server 2012r2 still listening on port 23

How else can I disable telnet to comply with a security audit? The Telnet services roles are not enabled on this server. But it is LISTENING at 0.0.0.0:23. Also there is no local windows firewall to ...
0 votes
0 answers
305 views

Azure VM, unable to connect from internet on ports configured (9089-9095)

I have created a VM on Azure with below steps:- Created VM Assigned a public static IP Created a new Virtual Network (Subnet default - (10.0.0.0/24) Did not create a NSG initially (NIC NSG was NONE - ...
0 votes
0 answers
579 views

Host is not resolved but connecting via telnet, can somebody explain how?

In aws ec2 instance, rds host name is not resolved by ping or nslookup but it is still able to reach via telnet or nc how ? ~# nslookup xxxx.rds.amazonaws.com nslookup: can't resolve '(null)': Name ...
1 vote
1 answer
1k views

How to connect to mail.hotmail.com via port 25 from DNS as instructed by Outlook

If you read https://sendersupport.olc.protection.outlook.com/pm/troubleshooting.aspx, it says Confirm that your DNS is set up correctly Try connecting to mail.hotmail.com via port 25. If you are ...
0 votes
1 answer
155 views

Is there a "server" version of telnet? [closed]

If I want to quickly connect to a socket as a client and type something I can use telnet. Is there a version of telnet or a similar program that provides the server-side of this? In other words, is ...
2 votes
1 answer
5k views

How can I disable sending mail through postfix smtp without auth

I just setup a mail server with postfix 2.6.6 and dovecot. I have the auth related config in main.cf like below: smtpd_tls_cert_file=/etc/httpd/ssl/mail.crt smtpd_tls_key_file=/etc/httpd/ssl/mail....
3 votes
3 answers
4k views

telnet non interactive: connection closed by foreign host

if I do telnet host_ip port < /dev/null Trying host_ip... Connected to host_ip. Escape character is '^]'. Connection closed by foreign host. By checking the wireshark, the client side sends tcp ...
0 votes
1 answer
203 views

how to build a telnet middleware server

I need to comunicate an old crm system with a new asset. Crm system can only send fixed commans over telnet connection but this new asset can only receibe commands via api rest. Im planning to ...
1 vote
1 answer
145 views

Service sometimes working, sometimes not working

I want to connect Centos B's 33060 port from Centos A. I can ping Server B. [root@serverb ~]# ping 10.42.40.182 PING 10.42.40.182 (10.42.40.182) 56(84) bytes of data. 64 bytes from 10.42.40.182: ...
4 votes
4 answers
17k views

How to forward UDP Wake-on-Lan port to broadcast IP with IPTABLES?

I'm trying to setup Wake-on-Lan for some of the LAN computers at home and it seems that I need to open a UDP port (7 or 9 being the most common) and forward all requests to the broadcast IP, which in ...
0 votes
1 answer
6k views

Execute command on LINUX via PUTTY from Windows [duplicate]

I want to open a putty session (SSH) from command line and immediately execute on the remote machine a specific command. Something like: putty.exe -ssh user@host -pw pass123 < "cd /some/...

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