[SOLVED] [LINUX] telnet: connect to address 127.0.0.1: Connection refused

thomas2004ch · 03-24-2015, 07:26 AM

Hi,

I have problem by sending email. So I try the following:

Code:

telnet localhost 25

But I got error as follow:

Code:

Trying 127.0.0.1...
telnet: connect to address 127.0.0.1: Connection refused

The content of the /etc/hosts is follow:

Code:

]# cat /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1               localhost.localdomain localhost
::1             localhost6.localdomain6 localhost6

What could be the reason?

TenTenths · 03-24-2015, 07:29 AM

sendmail/postfix not running or not configured to listen on localhost

MensaWater · 03-24-2015, 07:32 AM

The most obvious would be that port 25 isn't LISTENing.

Run "lsof -i :25" to see if it is. Typically you'd need a mail program like Sendmail or Postfix to be LISTENing on that port.

If mail is LISTENing you'd want to make sure the port shown by lsof is *:25 (for all interfaces) or 127.0.0.1:25 (or localhost:25) for just localhost.

If the port is LISTENing you'd need to make sure the configuration of your mail program is allowing connections on localhost (which most do by default).

thomas2004ch · 03-24-2015, 07:38 AM

As I run the " lsof -i :25", I got nothing. This means there is problem?

But the other machine where the telnet works, I got response as follow:

Code:

]# lsof -i :25
COMMAND   PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
master   2745 root   11u  IPv4   9936      0t0  TCP localhost.localdomain:smtp (LISTEN)
java    15132 root  589u  IPv4 325729      0t0  TCP localhost.localdomain:36848->localhost.localdomain:smtp (ESTABLISHED)
java    15132 root  593u  IPv4 323371      0t0  TCP localhost.localdomain:36812->localhost.localdomain:smtp (ESTABLISHED)

thomas2004ch · 03-24-2015, 07:40 AM

Quote:

Originally Posted by TenTenths

sendmail/postfix not running or not configured to listen on localhost

which postfix do you mean?

TenTenths · 03-24-2015, 08:39 AM

Quote:

Originally Posted by thomas2004ch

which postfix do you mean?

postfix the main alternative mail server to sendmail

thomas2004ch · 03-24-2015, 09:09 AM

Quote:

Originally Posted by TenTenths

postfix the main alternative mail server to sendmail

where locate this file? I find there are several postfix files. But which one should I look into?

TenTenths · 03-24-2015, 09:19 AM

First of all check which mail server you think should be running.

If it's postfix then google it, there's tons of help and how-tos around.

The main config file is main.cf

MensaWater · 03-24-2015, 09:22 AM

smtp = port 25 (you can verify that by typing "grep smtp /etc/services")

This means your lsof output confirms that localhost is LISTENing on port 25.

Your lsof output also shows you have to java processes connected (ESTABLISHED) to port 25.

In lsof it tells you the LISTENing process is called "master" and its Process ID (PID) is 2745. You can do "ps -ef |grep 2745" to see more details about that process and any parents or children it has. You can also get details in /proc/2745 about the process including its full path (if not shown in the grep).

master is the name of the main Postfix mailer daemon. You can see more details about it at:
http://linux.die.net/man/5/master

thomas2004ch · 03-25-2015, 02:29 AM

Many thanks for your detail info.

I've tried the 'grep smtp /etc/services' and I get:

Code:

# grep smtp /etc/services
smtp            25/tcp          mail
smtp            25/udp          mail
smtps           465/tcp                         # SMTP over SSL (TLS)
rsmtp           2390/tcp                        # RSMTP
rsmtp           2390/udp                        # RSMTP

Seems ok, since I get the same from another machine where the telnet works.

And I tired 'ps -ef |grep 2745' and I get:

Code:

# ps -ef |grep 2745
root      8813  6541  0 08:29 pts/0    00:00:00 grep 2745

This should ok as well? But where could be the probelm?

thomas2004ch · 03-25-2015, 02:48 AM

Besides, as I run command 'netstat -ntpl |grep "127.0.0.1"', I got

Code:

# netstat -ntpl  |grep "127.0.0.1"
tcp        0      0 127.0.0.1:2528              0.0.0.0:*                   LISTEN      32065/java
tcp        0      0 127.0.0.1:4449              0.0.0.0:*                   LISTEN      32065/java
tcp        0      0 127.0.0.1:7079              0.0.0.0:*                   LISTEN      32065/java
tcp        0      0 127.0.0.1:4455              0.0.0.0:*                   LISTEN      32065/java
tcp        0      0 127.0.0.1:6990              0.0.0.0:*                   LISTEN      32065/java
tcp        0      0 127.0.0.1:3447              0.0.0.0:*                   LISTEN      32065/java
tcp        0      0 127.0.0.1:6999              0.0.0.0:*                   LISTEN      32065/java
tcp        0      0 127.0.0.1:631               0.0.0.0:*                   LISTEN      2791/cupsd

Seems the port 25 is not opened.

By another machine I got:

Code:

]# netstat -ntpl  |grep "127.0.0.1"
...
tcp        0      0 127.0.0.1:3447              0.0.0.0:*                   LISTEN      21687/java
tcp        0      0 127.0.0.1:25                0.0.0.0:*                   LISTEN      2745/master

One can see the port 25 is opened.

TenTenths · 03-25-2015, 02:59 AM

Quote:

Originally Posted by thomas2004ch

As I run the " lsof -i :25", I got nothing. This means there is problem?

Yes, it means you don't have a mail server running.

Quote:

Originally Posted by thomas2004ch

Many thanks for your detail info.

I've tried the 'grep smtp /etc/services' and I get:

Code:

 # grep smtp /etc/services
 smtp            25/tcp          mail
 smtp            25/udp          mail
 smtps           465/tcp                         # SMTP over SSL (TLS)
 rsmtp           2390/tcp                        # RSMTP
 rsmtp           2390/udp                        # RSMTP

Seems ok, since I get the same from another machine where the telnet works.

/etc/services is just a list of services and port numbers it will be pretty much identical on any machine. It has nothing to do with whether a service is running or not.

Quote:

Originally Posted by thomas2004ch

And I tired 'ps -ef |grep 2745' and I get:

Which is the same process number in MensaWater's post. My guess is that you just copied and pasted his example which will be irrelevant on your machine.

Another way you can verify you have a mail server running by checking to see if there are any processes listening on port 25

Code:

netstat -lnp | grep 25

If you see something like this:

Code:

tcp        0      0 127.0.0.1:25                0.0.0.0:*                   LISTEN      1848/master

This means that POSTFIX is running and listening for mail on port 25. The process id (pid) is 1848.

If you see something like this:

Code:

tcp        0      0 127.0.0.1:25                0.0.0.0:*                   LISTEN      1139/sendmail

This means that SENDMAIL is running and listening for mail on port 25. The process id (pid) is 1139

If you don't get one of these two results then it's likely you don't have a mail server running.

For your next post let us know what Linux distro you are using. If you set it up yourself are you sure you installed a mail server and set it to run on startup?

thomas2004ch · 03-25-2015, 03:21 AM

Many thanks for the detail info.

I tried your command 'netstat -lnp | grep 25' and get:

Code:

# netstat -lnp | grep 25
tcp        0      0 127.0.0.1:2528              0.0.0.0:*                   LISTEN      32065/java
udp        0      0 fe80::250:56ff:feaf:2a1b:123 :::*                                    2812/ntpd

This means no mail service is running?

Following is the OS:

Code:

# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 5.11 (Tikanga)

The configuration on this machine is not done by me.

TenTenths · 03-25-2015, 03:28 AM

Quote:

Originally Posted by thomas2004ch

This means no mail service is running?

Correct.

Quote:

Originally Posted by thomas2004ch

The configuration on this machine is not done by me.

So are you now responsible for admin on it?

Try this:

Code:

chkconfig --list

and see if you can see entries for either POSTFIX or SENDMAIL in the first column.

If you see entries and then things like 0

ff and all 0-6 are

ff then it's likely that a mailer is installed but not working.

Depending on your infrastructure you may have another server that acts as a mail server for the rest of your environment, if that's the case then you should be configuring your mail client or application to use that server rather than "localhost".

thomas2004ch · 03-25-2015, 03:34 AM

I did further 'chkconfig --list' and I can see postfix is turned on. But as I run 'service postfix status', it shows nothing. Then I try 'service postfix start' and still nothing happens. This means the postfix is deffect.

I am not the admin. But I just told this to the admin. Hope he can repare this.