Questions tagged [port]

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With netcat how to safely open an external port to the Internet

I have found the perfect solution to write scripts which send files across machines over the Internet using netcat. On the machine receiving files I do nc -l -p 1234 -k and then on the machines ...
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1answer
31 views

Why does SELinux (with Enforcing=1) allow binding to low (or any) ports, by default?

I assume that Selinux defaults, based on the documentation, mandate that basically all port operations would be blocked and logged as AVCs. I have an SELinux enforcing enabled VM, created with ...
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31 views

Cannot change httpd listen port on anything other than 80 [closed]

EDIT: Nevermind, it was a selinux issue. So I set up an apache server on an aws instance running rhel 7.6. Whenever I change the listen port from /etc/httpd/conf/httpd.conf to anything other than 80,...
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0answers
17 views

Identify devices connected to the COM port in Ubuntu [duplicate]

I need to create an application that could identify the devices that are connected through the COM port of an Ubuntu system. I've checked out a lot of codes and also tried to use them but I couldn't ...
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1answer
38 views

IPTABLES - Not able to open Ports

since i couldn't find anything that explains me what I am doing wrong I hope you guys can help. I got a Ubuntu 18.04 server running. I want to open Port 9987 (just an example) so i Tried to add it to ...
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3answers
60 views

KDE Connect Not Working [Ubuntu 16.04] : KDE Connect is not discovering phone and vice versa

I have installed the KDE Connect application on my desktop and on my phone [Xiaomi Redmi 3S Prime]. However the desktop application would not detect my phone and vice versa. I have checked the ports. ...
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0answers
33 views

Cannot open/access ports on Ubuntu

I created an Apache web server on Ubuntu 18.04.2 LTS, using the guide described here. Afterwards the web server worked completely fine. Later on I installed Libvirt onto the web server, after which ...
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14 views

Embedding in iframe web-application at a port on another application in the same server

I have an application at say port 5000 which can render embedded iframes. https://host-public-ip:5000/ I have a second application on say port 6000. I would like to embed this page in an iframe in ...
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1answer
34 views

Understanding the Netcat properly [closed]

Netcat confuses me a little bit and here are the reasons: when I run: nmap localhost There are some ports listed with the information whether they are open or closed. So if I run the command : nc -l -...
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1answer
23 views

SSH Tunneling, have some problems [closed]

I have a computer and host A, B. Host A has internet connection and host B placed in host's A local network. Host B has Web Interface at port 8080. I need to forward port on host A. And then i want to ...
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1answer
25 views

How to open a port to specific IPs in iptables while using docker?

I have a postgreSQL database inside of Docker that I don't want to expose it to the host network as it causes all users to see the exposed database port. (For now I don't have a pfsense or anything ...
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215 views

VSFTPD refuses to list directory when PASV is enabled

I'm configuring VSFTPD on Ubuntu 18.04 and have followed all the guidelines. It's working OK for plain FTP (insecure), however as soon as I enable SSL/TLS and Passive mode, it connects, but I am ...
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2answers
88 views

When does `[::]` or `0.0.0.0` mean this network and when this host? [duplicate]

Tanenbaum's Computer Networks says The IP address 0.0.0.0, the lowest address, is used by hosts when they are being booted. It means ‘‘this network’’ or ‘‘this host.’’ [::] is IPv6 version of ...
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1answer
50 views

Does `rpcinfo` list the port number of a RPC service?

$ rpcinfo program version netid address service owner 100000 4 tcp6 ::.0.111 portmapper superuser 100000 3 tcp6 ::.0.111 ...
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1answer
86 views

Why does postgresql server have a `localhost:57504` to `localhost:57504` UDP “connection”?

$ sudo netstat -ap | grep postg tcp 0 0 localhost:postgresql 0.0.0.0:* LISTEN 1567/postgres udp 0 0 localhost:57504 localhost:57504 ...
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1answer
46 views

Why is mysql server accepting nonlocal request, while postgresql server is not?

By default configurations, why is mysql server accepting nonlocal request, while postgresql server is not? $ nmap -p0-65535 192.168.1.97 Starting Nmap 7.60 ( https://nmap.org ) at 2019-03-20 14:34 ...
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36 views

Why can't `lsof` report some open port's information? [duplicate]

I am running this with the IP address of the same machine: $ nmap -p0-65535 192.168.1.198 Starting Nmap 7.60 ( https://nmap.org ) at 2019-03-20 10:13 EDT Nmap scan report for olive.fios-router.home (...
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23 views

writing data out to already opened port

I have a setup in which one unix program (s51 from a microcontroller simulation package) is a server tied to a specific port. Let's call the port 111. I also have setup a client on the same computer ...
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1answer
57 views

Red Hat Linux - port is in listening state but could not find process ID

I have this problem for my application, port is in listening state but process ID is not showing up. Used below commands. This is cloud AWS server Red Hat Linux. $ netstat -tulpn tcp 0 ...
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66 views

send hex as characters to output to remote end

I'm doing a project for a microcontroller that involves sending and receiving special (non-printable character) data through its serial port. I found myself a simulator (ucsim) so I can test things ...
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1answer
36 views

Can't access SNMP stack on rasp pi through router from WAN

Background I am running the following On my laptop the very latest version of arch linux with all the latest updates. It is from this laptop that I am querying an SNMP stack on a rasp pi $ uname -...
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2answers
220 views

Linux's Internet domain socket, transport protocols (TCP/UDP)'s socket and port

I have been bothered for a long while by some confusions among internet domain socket provided by Linux, transport protocols (TCP/UDP)'s socket and transport protocols (TCP/UDP)'s port. ...
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0answers
91 views

Why there are 65535 ports [closed]

Wondering why they chose to have 16-bit (65535) ports. Why not just 256 or millions. I understand it's a power of 2, but not why it was this size. Wondering in what situations it would make sense to ...
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0answers
16 views

Can't connect to OpenLDAP

i have installed iRedMail with OpenLDAP managing the Mail Accounts. So far that works. Now I wan't to connect other applications to that LDAP and I'm trying to use a LDAP Explorer "LDAP Admin" for ...
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1answer
39 views

Is there a way to figure out what physical port a drive is being inserted into through linux?

Without knowing the order of which drives are being inserted and which ports they are being inserted (by human eye), is there a way to tell where they are being inserted using linux commands? I need ...
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1answer
51 views

Open port 4000 for Trader Workstation in Fedora

I have installed Trader WorkStation by Interactive Brokers. However, the program does not run, with assistance from support I found that the firewall is the problem. The servers (several primary and ...
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0answers
14 views

OpenVPN Gateway with Killswitch and Prerouting Ports

My Prerouting in UFW Doesnt work. I´m using an VPN Connection via tun0. Internet Connections via tun0 as a gateway works but not the Port Forwarding. im on debian Strech 9 UFW Before Rules. Only ...
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1answer
296 views

iptables priority

After deploying all kubernetes ressources I wanna open port 443. I added it to my whitelist table but it is still closed. Same already happened to me for port 80. After flushing all tables, deleting ...
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2answers
79 views

How make a port appear open with an nmap scan

To avoid someone knowing which port are open on my machine, I thought it would useful to open all unused port so that the nmaper is unable to identify which port are really open. How make a port ...
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1answer
45 views

Networking: port listening but nc fails

I have set up a docker-compose stack on a server. One of its services is jaeger collector and is configured as follows: collector: image: jaegertracing/jaeger-collector:1.8 environment: ...
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1answer
30 views

One port is listening with an * and the other is listening with 127.0.0.1 and only the first is accepting remote connections

Please see the attached picture below, and then I will explain: So, I have Solr running which uses port 8983. And as you can see in the screen shot, it's listed as "TCP *:8983 (LISTEN)". And, it's ...
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2answers
131 views

port 1556 listening on tcp6 causing issues

on my RedHat 7, i noticed that network connection for Netbackup stopped working and i tried everything including rurning off my firewall and disabled SELINUX with no luck. the only thing i noticed ...
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1answer
90 views

How to close nc port in Debian 9?

I am struggling to close these ports which seem to be backdoors -- or at least I have never opened and used them. How can I close or shutdown nc and close these ports? netstat -lntup | grep nc ps-...
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1answer
42 views

Restrict inbound access on localhost:TCP port

For reasons beyond my control, I have a binary that binds to TCP "localhost:$PORT". (Unix socket bindings would make this question moot). If I understand correctly, this means that although no ...
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1answer
41 views

Blocking ports with iptables 1.4.2

I am trying to block some ports on an embeded uClinux· The Iptables version is 1.4.2. The command I used was iptables -I INPUT -p tcp --dport 22 -j DROP But it seems that iptables 1.4.2 is not ...
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2answers
84 views

Telnet - how to verify why a port is blocked?

We have linux machines with RedHat 6.5 operating system. When we try to telnet to localhost on port 8182, we get connection refused: service iptables status Firewall is not running telnet localhost ...
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1answer
384 views

nginx: Can't bind to port (already in use) although no tasks running on that port [closed]

i just chose nginx for my webserver and I did follow this tutorial: https://github.com/groovemonkey/hands_on_linux-self_hosted_wordpress_for_linux_beginners However, I just can't connect to my ...
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2answers
910 views

SSH Remote port forwarding with multiple ports

For those who worked with ssh port forwarding or for those who have an idea, I managed to create a remote tunnel from my PC to a remote machine(a camera that does not have a public address) through a ...
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2answers
194 views

iptables allow everything, is it safe?

The os is Ubuntu Server 18 and I am running a web server on it. Is it safe to accept all traffic on all ports? iptables -P INPUT ACCEPT iptables -P FORWARD ACCEPT iptables -P OUTPUT ACCEPT I tried ...
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2answers
5k views

How to check which localhost's ports are used on the terminal? [closed]

I'm working on the Linux Ubuntu terminal and I'm wondering how to check directly on terminal which localhost ports are used please ?
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1answer
103 views

Which ephemeral ports are used with raw sockets

Referring to How source ports get assigned, I do know, how the local port is determined. (=> Random free ephemeral port). However, why does my raw socket using socket(AF_INET, SOCK_RAW, IPPROTO_TCP) ...
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2answers
782 views

systemd opens socket, service fails to bind to this socket

I am working on RedHat7.5. I made a systemd socket (/etc/systemd/system/barfoo.socket): [Unit] Description=This is the barfoo socket [Socket] ListenStream=0.0.0.0:123 NoDelay=true BindIPv6Only=both ...
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1answer
306 views

IPv4 and IPv6 sockets with same port

Is it possible to have a single process that would have two sockets, one using the AF_INET and one using the AF_INET6 families, while both being bound to the same port number, e.g. 20000? If the IPv6 ...
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1answer
239 views

Chainging proxychains DNS port

I am using a proxychains on Kali with a DNSCrypt nameserver which operates on port 443. When I start proxychains it tries to connect to the DNS server on port 53 and it returns a timeout. How can I ...
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2answers
90 views

remap port 80 to 22

I would like to remap incoming requests on port 80 to port 22 and tried the following: sudo iptables -A PREROUTING -t nat -p tcp --dport 80 -j REDIRECT --to-ports 22 but still, ssh -i key user@host -p ...
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0answers
20 views

Regulating user-daemons from listening on unprivileged ports (preventing server spoofing)?

If I have a port >1024 but that I want to reserve to one executable how can I ensure that no other executable can open and listen to a socket on that port? /usr/bin/foo_srv -p 8080 /usr/bin/bar_srv -...
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1answer
40 views

How to change the port number for any service? [closed]

I know how to change the port number through the config file of sshd but I want to know how do you change any port number for any service without going into the sshd condfig file or for any service in ...
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3answers
1k views

Port open/listen but no associated process

In the output of nmap -p- localhost I get an unknown open tcp port, that's different at each reboot. How can I determine which process opened it and listens through it. I tried many of the usual tools ...
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1answer
68 views

How to open up a tcp server compatible with tcpgoon

I have tcpgoon installed on one computer, provided that there is a direct VLAN connection, how do I create a TCP server on my second computer?
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5answers
4k views

How do I get only the PID, without any extra information, of a process running on port 3000?

I'm using CentOS 7. I want to get the PID (if one exists) of the process running on port 3000. I would like to get this PID for the purposes of saving it to a variable in a shell script. So far I ...