Ubuntu Networking :: How To Determine Which Port Needs Opening
Aug 2, 2011
I am unable to open my webmail on my small business computers (all ubuntu 10.04 LTS using a Billion router) but am able to access it from my home computers (also ubuntu 10.04 LTS but with a different router).
The most likely problem is obviously that the firewall in the router is blocking access. I know how to open ports in the router's firewall, but how do I determine which port or ports need to be opened?
I have asked my email provider, and that have replied that the port can vary and I need to get my technical support people to do it. Obviously they struggle to understand the concept of 'small business"!
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May 30, 2011
I'm fairly sure that this is an Ubuntu issue, as I've tried this on my windows computer with success.I'm running a minecraft server on my laptop, previously over a wireless connection but the data rates were too slow. On a wired connection, however, the server starts up and runs like normal but the port is not open when accessing from the network's public IP. I tested this with canyouseeme(.)org. I can get to it from other computers within the network by using a local IP, which to me seems a little strange as it seems to indicate that the port is open on the PC but somewhere in the router it gets confused due to being wired(?). Obviously I've forwarded the ports on the router (BTHomehub 2.0) with both TCP and UCP (it worked over wireless!). Any suggestions as to what might be causing this? I'm stumped.
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Apr 27, 2011
I'm trying to open up some ports to connect via vnc to a server running Centos 5.5. I've edited /etc/sysconfig/iptables everything *looks* fine, but I still can't seem to get access to the port I've opened (I added some newlines for clarity between commands):
[Code]....
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Jan 16, 2011
I'm developing a serial port application under Lazarus using the SunaSer code library.
The application reports an error indicating that "the Port is opened by another process".
What command can I execute in a Terminal session to determine what process has the USB-serial port open?
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May 18, 2010
Finding the process that is using a certain port in linux
I have an Ubuntu Server setup, where I'm trying to set up a daemon that wants to have access to port 8080. When I run the command, the error message says it's being used by another process. But which one, it doesn't say. How can I go about finding which program uses this port?
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Jan 21, 2010
Is there a way to determine what program is listening to some port, TCP or UDP, in Linux?
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Jan 28, 2011
I am trying to run a minecraft server from my slackware machine, but i am having an issue.The port for minecraft (25565) is open on my router, but it is reported as closed by all the open port check tools. I noticed that the same was happening for my VNC server. the port reports itself as closed until i actually open the vnc server software. for examplei check the vnc port (5900) when the vnc software is not running, and it is reported as closed. nmap localhost gives the following:
Code:
Not shown: 993 closed ports
PORT STATE SERVICE
[code]....
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Oct 11, 2010
I'm thinking about making a web server but, I have an issue:will opening Port 80 affect all computers on a network?
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Dec 24, 2010
I'm trying to open port 119. I already have a few ports open. I've used webmin to open both incoming and outgoing ports. iptables --list --numeric gives me:
Code:
...
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:10000
[code]....
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Aug 17, 2010
I'm trying to open ttySx from an interrupt.the kernel crashes. is it possible to open/write to serial port from interrupts ? I think it crushes because when I try to open the device there is a mutex lock which cause the kernel to crash , am I right
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Feb 18, 2010
I want to do a simple port redirect, i.e. whatever comes trough whatever interface on port AAAA will get redirected to port BBBBI thought that iptables -t nat -I PREROUTING --source 0/0 --destination 0/0 -p tcp --dport AAAA -j REDIRECT --to-ports BBBBhowever it doesn't work, e.g. nc -v -w2 -z localhost AAAA gives:
nc: connect to localhost port AAAA (tcp) failed: Connection refused
while
nc -v -w2 -z localhost BBBB
[code]....
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Jun 6, 2011
i have a proxy server up and running but one server using port 8181 cannot be accessed.how i can open that port!...i tried adding it in the safe ports but it still isn't working...
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Jul 18, 2011
Im having a frustrating issue with my two machine cluster I setup using Conga. Everything was working great except now when lucci starts mysql the port (3306) is never opened to outside machines. I can do a "ps -ef | grep mysql" and see it running as well as login to mysql on the node it is running on - but an nmap of the machine does not show the 3306 port and I cannot login to mysql remotely and yes I turned off all iptables(iptables,ip6tables) and SElinux is disabled.What am I missing here? If I start mysql on my own (and it is using the same my.cnf as lucci is) it does show the port open and works perfect,t for some reason when lucci starts it, no dice
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Aug 7, 2010
When I use the following command:
ssh user@ssh_server -L 5500:localhost:5500 -p 22
everything works fine. I can log in, and local port forwarding is done. Otherwise when I use the command:
ssh user@ssh_server -R 5500:localhost:5500 -p 22
I get an error "remote port forwarding failed for listen port 5500". However when I try remote port forwarding in WinXP by use of putty there is no problem...
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Jul 14, 2011
I want to set my ip as static and port forward it through a specific port can anyone help me with this im using ubuntu 10 with 64 bit OS
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Apr 4, 2011
I'm trying to use iptables in order to forward all the incoming packets for port 5555 to port 5556 on the same server (192.168.2.101).
I wrote the following commands:
iptables -A PREROUTING -t nat -i any -p tcp --dport 5555 -j DNAT --to 192.168.2.101:5556
iptables -A FORWARD -p tcp -m state --state NEW -d 192.168.2.101 --dport 5556 -j ACCEPT
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Feb 20, 2010
I'm using a Debian servers, as router/firwall.. I've two ethernet interfaces into the server, one for wan and one for lan. The i use SNAT so my LAN clients can access the internet throgh the debian router. That is working... Now i want to be able to access servers on the LAN site from the WAN site, and i wanna use port address translation (PAT). I have a FTP server running on a lan server, so i'm trying to portward port 21.
iptables -t nat -A PREROUTING -p tcp -i eth1 -d (WANIP) --dport 21 -j DNAT --to 192.168.1.2:21
When people try to access my FTP from the WAN site, they are redirected to the local FTP server, and they are promted for crendentials, but when the credentials are typed, and the local ftp server should answer the wan request, the connections dies.
The wan clients are being promted for credentials, so they are redirected to the local lan server, but after that the connections dies, so i think there is some kind of nat problem, when the local lan server is trying to respond to the wan request..
Here i my iptables script:
#flush table
iptables -F
#input regler
[code]....
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Feb 12, 2009
I make an application on GNU/Linux which listening on a MULTICAST stream, so I open my unconnected socket, bind it on a MULTICAST address and a port, join the multicast group with the "setsockopt (IP_ADD_MEMBERSHIP)", then I receive datagram on my socket.
Now I've two different instances of the same application that run with their own MULTICAST address and port. And what I found strange is that, after a misconfiguration, I switch the ports, for example:
Emitting on 225.0.0.1/23451 and 225.0.0.2/23452
Receiving on 225.0.0.1/23452 and 225.0.0.2/23451
And my receiving part doesn't care about the MULTICAST address, it looks like the socket is listening on the port number only! I mean that the receiver [225.0.0.1/23452] take its datagrams from emitter [225.0.0.2/23452] and vice-versa!
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Apr 25, 2009
How can i redirect data received on a port to another port located in a different machine? Can i do this using IPTABLES ?
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Mar 25, 2010
I have a mail server on which I would like to block port 25 on my eth0 for everyone except our external spam filter. the problem is that I want our users to be able to connect via port 10025 which is forwarded to port 25, which then is blocked...
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Oct 24, 2010
I had to add them to my firewall script when I installed openvpn on my dd-wrt router:
iptables -I FORWARD -i br0 -o tun0 -j ACCEPT
iptables -I FORWARD -i tun0 -o br0 -j ACCEPT
iptables -I INPUT -i tun0 -j REJECT
iptables -t nat -A POSTROUTING -o tun0 -j MASQUERADE
what should I add/change to set up port forwarding of port 1000 to ip 192.168.1.200. also how to get the answer sent by 192.168.1.200 follow the same route used by the data received through port forwarding.
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Apr 20, 2010
How can I send out a broadcast from one device to the other machines on the LAN to reply with their operating system.
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Jul 14, 2011
My laptop has an internal wireless g "adapter" (for lack of a better word) and I plugged in a very cheap and very small ASUS wireless N adapter later on. The ASUS adapter has better bandwidth (again for lack of a better word) but isn't as high quality of a link as the internal adapter is.The laptop appears to be using the internal adapter, but i want it to use the ASUS adapter.
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Aug 1, 2011
In the terminal, what command can I use to find out the current ip address that my ISP allocates to me from their server to my router?
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Aug 30, 2010
i have an embbeded hardware that uses bootp for booting from a Network Managemnt Host (NMH)on the same ethernet. The embedded hardware has both kind of ports i.e ethernet as well as E1/T1. I would like ask, what do i require to establish a communication-link between the embedded hardware and the NMH throuh E1/T1 ports of embedded hardware, so as to make it boot through from E1/T1. Further, NMH possesses only ethernet port. Just to refine my questions i'd like to know what additions do i need to do on my NMH , like may be i have to put an E1/T1 port or is it possible that the E1/T1 port can be directly connected to an ethernet port on the other host.
pardon me if i am not making absolute sense here as my knowledge is limited on Layer 1 and layer 2.
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Aug 23, 2010
how to access networking port and run scripts on that port so as to gain access of remote machine.is that possible through command prompt or through software.
i kno ip address of my frnd who is chattin with me .okay.i want to run an application on his computer .i came to kno tht we can run script o through port
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Jan 8, 2010
i want to change the mtu size of my ethernet controller. I have done successfully set the mtu size 9000 for broadcom net xtreme PCI: 66 Mhz 64 bit 1 gigabit card. (fibre)
Part model no: BCM95703A31
[root@lux08 ~]# ethtool eth0Settings for eth0:
Supported ports: [ FIBRE ]
Supported link modes: 1000baseT/Half 1000baseT/Full
Supports auto-negotiation: Yes
[Code]....
how to change the mtu size for this NIC?
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Apr 5, 2010
I'm running a dual boot system at work. I'm connected to a few shared drives in XP, and would also like to connect to them while using Ubuntu.How do I determine the addresses of the servers I'm connected (mapped) to in XP?
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Apr 6, 2009
I'm just an undergrad with duck tape and google searches to hold this place together. Anyways on to my question. Where I work, we have a tape library but no way to configure it, the backup software simply talks to the robot to load and unload tapes. There is a network port on the library and I do have the software, but have been running into problems getting access. I was wondering, is there a way to determine the ip address of this machine by plugging in a cross over cable with a laptop and scanning it? What tools could I use to do this?
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Dec 7, 2008
I am looking for a command which, when typed from the command line, returns the ip-addresses of the DNS nameservers that my ISP is using.I think is should be technically possible to write a program that does this, because linux installers set up /etc/resolv.conf correctly (as does knoppix). But I've been unable to find a command that does it. Is there one, and if so, what is it called?
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