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What is an origin and solution for "port 9000: Connection refused" error?

rated 0 times [ 0] [ 0] / answers: 1 / hits: 36851 / 3 Years ago, wed, july 28, 2021, 7:51:07

I am stuggeling with port 9000: Connection refused error.

I work on Ubuntu 14.04 and faced the problem when trying to run Hadoop in a non-distributed mode, as a single Java process (compare Hadoop 2.4.1 documentation). I tried to follow Hadoop Wiki suggestions on this error (hadoop/ConnectionRefused) but I did not succed (I am a beginner Ubuntu user and find it difficult even to 100% understand the suggestions given). I posted a stackoverflow question from which I conclude that I have some general problem with port 9000 Connection.

telnet output:

martakarass@marta-komputer:~$ telnet localhost 9000

Trying 127.0.0.1...

telnet: Unable to connect to remote host: Connection refused

nmap output:

martakarass@marta-komputer:~$ nmap localhost



Starting Nmap 6.40 ( http://nmap.org ) at 2015-04-27 11:09 CEST

Nmap scan report for localhost (127.0.0.1)

Host is up (0.00022s latency).

Not shown: 995 closed ports

PORT    STATE SERVICE

22/tcp  open  ssh

139/tcp open  netbios-ssn

445/tcp open  microsoft-ds

631/tcp open  ipp

902/tcp open  iss-realsecure



Nmap done: 1 IP address (1 host up) scanned in 0.08 seconds

Netcat configuration:

I tried to make use of the following command to force the 9000 port to be open:

nc -k -l 9000

but it did not work well (I was still not able to perform the standlone operation mentioned and linked above).

Judging from my google research results, I see that the problem is quite common and poses a huge struggle especially for those who are not good at "admin-job-related issues". As I belong to those, I kindly ask for answers to the following questions:

Q1: What is the origin of such problem in general? (Some for a layman introductory words / references about basic issues connected to ports / connections etc. would be very very welome).

Q2: How to deal with this problem?

Update.

sudo netstat -nlp | grep :9000

returns nothing.

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eighethod

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2 Years ago

answered 3 Years ago hergy · Accepted Answer

Eventually, I managed to make my service listen to the port 9000 by adding to the /etc/ssh/sshd_config file the following line:

Port 9000

I followed this serverguide/openssh-server (it contains also some important remarks about making a copy of the original file, restarting the sshd server application etc.)

After this I can see:

telnet output:

martakarass@marta-komputer:~$ telnet localhost 9000

Trying 127.0.0.1...

Connected to localhost.

nmap output:

martakarass@marta-komputer:~$ nmap localhost



Starting Nmap 6.40 ( http://nmap.org ) at 2015-05-01 18:28 CEST

Nmap scan report for localhost (127.0.0.1)

Host is up (0.00023s latency).

Not shown: 994 closed ports

PORT     STATE SERVICE

22/tcp   open  ssh

139/tcp  open  netbios-ssn

445/tcp  open  microsoft-ds

631/tcp  open  ipp

902/tcp  open  iss-realsecure

9000/tcp open  cslistener



Nmap done: 1 IP address (1 host up) scanned in 0.05 seconds

netstat output:

martakarass@marta-komputer:~$ sudo netstat -nlp | grep :9000

tcp        0      0 0.0.0.0:9000            0.0.0.0:*               LISTEN      16397/sshd      

tcp6       0      0 :::9000                 :::*                    LISTEN      16397/sshd