Use the codelsof/code command. To find which process(es) IDs listen on port 80: codesudo lsof -i -P grep 80 /code codesudo netstat -program -an grep 8888/code You should see the PIDs displayed. You can certainly use the coden. I currently have ftp running on a Mac OS X 10.3.9 server. On my firewall I am port forwarding port 21 to that server and everything is working fine. I'm concerned about security and in lieu of changing to something like sftp, I'd like to use a non standard port for ftp requests.
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␡- Why Use Port Forwarding?
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Although VPN solutions are great for securely connecting to and accessing resources on remote networks, they require some expense and setup. When you only occasionally need to securely access a remote Mac OS X computer, server, or even a whole network, you can use a technique called SSH port forwarding to create secure connections to access specific types of resources. This gives you many of the benefits of VPN but without the cost or effort of creating a permanent VPN solution. In this final article on his series on VPN setup for Mac OS X and Mac OS X Server, Ryan Faas shows you how to configure and use port forwarding.
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The first two articles in this series looked at what Virtual Private Networks (VPN) technologies are available for Mac OS X and Mac OS X Server. Part 1 talked about how to configure Mac OS X computers to connect to remote networks using VPN. In part 2, we talked about how to configure the VPN service in Mac OS X Server. In this final piece, we look at how to use SSH’s port forwarding feature (also called port tunnelling) to achieve some of the benefits of VPN access without the need for a VPN server.
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SSH (secure shell) is a technology for securely connecting to a remote computer. As you might suspect from shell being in the name of the technology, SSH is primarily intended to allow shell login and command-line access to remote Unix or Linux computers (though SSH clients exist for Windows as well). This allows for administration and use of the remote computer as if you were entering commands from a keyboard attached to it. SSH uses encryption technology to establish secure connections between the two computers, which enables it to be far more secure than previous remote command-line features such as telnet.
The SSH protocol includes a number of other features besides basic login. One of them is port forwarding, which forwarding enables you to establish an SSH connection to a remote computer and then to forward specific types TCP/IP network traffic to that secure connection instead of to your computer’s network port, based on the port numbers associated with protocols used for that type of traffic. The result is that when you make requests for specific types of network resources, such as file sharing, your computer will forward those requests through the SSH connection instead of attempting to locate the resources on the local network to which your computer is connected.
Why Use Port Forwarding?
Port forwarding provides two main uses. First, it enables you to establish secure tunnels between two computers (much like VPN). You can securely connect to another computer through the Internet to securely transfer data that you might otherwise not be able to do. Any Internet or network protocol can be forwarded, including things like file sharing, web browsing, email, and remote management tools (such as Mac OS X Server’s Server Admin or the multiplatform VNC).
Second, you can use port forwarding as a way to allow secure access through a firewall. When you implement a firewall, one of the primary ways it secures your network or computer is by limiting what types of traffic can pass into the network. For every type of network or Internet protocol you allow, you need to open ports on the firewall. Each newly opened port exposes your network or computer to more potential security risks. This can be especially dangerous when you start opening ports used for remote management protocols such as Apple Remote Desktop, VNC, or the Mac OS X Server management tools. Port forwarding mitigates these risks because you need to open only a single port that SSH will use to forward all the other traffic through. You even get to choose the port that SSH uses, meaning that you can choose a port that is traditionally unused for network or Internet traffic.
VPN provides much of the same functionality by encrypting data and transmitting it through set ports the same way. However, implementing a VPN server can be expensive and require some amount of effort. There can be many situations in which you only want to establish a secure connection to transfer a handful or files, manage a remote server or workstation, or perform some other task very infrequently. A great example is when you’re at work and need access to a file from home (a situation opposite of the ones in which VPN is typically used), or if you want to control a friend’s computer securely using VNC to help them work on a project or resolve a problem.
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Information about these and other types of Mac ports is in the specifications for your Mac: Choose Apple menu > About This Mac, click Support, then click Specifications. Or check your Mac user guide.
Thunderbolt 3
Use Thunderbolt 3 with displays and other devices that connect using either a Thunderbolt 3 cable or USB-C cable. You can also connect a USB-C power adaptor and cable to charge your notebook computer. If you have a device that doesn't connect to this port, you might be able to use an adaptor to connect it.
These Mac models have Thunderbolt 3 ports:
- MacBook Pro introduced in 2016 or later
- MacBook Air introduced in 2018or later
- iMac introduced in 2017 or later
- iMac Pro (all models)
- Mac mini introduced in 2018
- Mac Pro introduced in 2019
If your Mac notebook or desktop computer has more than one port like this, each port supports ThunderBolt 3 and USB-C.
USB-C
Use USB-C with displays and other devices that connect using a USB-C cable. You can also connect a USB-C power adaptor and cable to charge your notebook computer. If you have a device that doesn't connect to this port, you might be able to use an adaptor to connect it.
MacBook models introduced in 2015 or later have a single USB-C port. This port doesn't support Thunderbolt devices.
If your Mac has only one port like this, it's a MacBook that supports USB-C but not Thunderbolt.
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Thunderbolt
Use Thunderbolt or Thunderbolt 2 with displays and other devices that connect using a Thunderbolt cable.
These Mac models have Thunderbolt or Thunderbolt 2 ports:
- MacBook Pro introduced in 2011 until 2015
- MacBook Air introduced in 2011 until 2017
- Mac mini introduced in 2011 until 2014
- iMac introduced in 2011 until 2015
- Mac Pro introduced in 2013
Thunderbolt and Thunderbolt 2 are not the same as Mini DisplayPort . They have the same shape, but use different symbols on the cable and port. However, this port does support Mini DisplayPort for video output, so you can use a Mini DisplayPort cable to connect a Mini DisplayPort display.
Mini DisplayPort
Use Mini DisplayPort with displays that connect using a Mini DisplayPort cable.
These Mac models have Mini DisplayPort:
- MacBook Pro introduced in late 2008 until 2010
- MacBook Air introduced in late 2008 until 2010
- Mac mini introduced in 2009 and 2010
- iMac introduced in 2009 and 2010
- Mac Pro introduced in 2009 until 2012
Mini DisplayPort is not the same as Thunderbolt or Thunderbolt 2 . They have the same shape, but use different symbols on the cable and port.
USB-A
Use USB-A with devices that connect using a USB cable. USB ports are sometimes known by the USB specification of the port, such as USB 2 or USB 3.
Left to right: power, two Thunderbolt, USB-A, and Audio-Out.
HDMI
Use HDMI with displays and TVs that connect using an HDMI cable.
Ethernet
Use Ethernet with networks and devices that connect using an Ethernet (RJ45) cable.
FireWire
Use FireWire with devices that connect using a FireWire 400 or FireWire 800 cable.
SD card
Use the SD card slot with SD, SDHC, SDXC, MMC and UHS-II media cards, such as those used by digital cameras.
Audio
Use Audio-Out — or — with headphones, speakers and other audio-output devices that connect using an audio cable that has a 3.5 mm (1/8 inch) audio jack.
Use Audio-In with a microphone or other audio-input device that connects using an audio cable that has a 3.5 mm (1/8 inch) audio jack.
Power
Use the power port , if available, to connect your computer to AC power using a MagSafe cable or adaptor. This port isn't available on newer Mac notebook computers, which use Thunderbolt 3 or USB-C for power and charging. Learn more about power adaptors and cables for Mac notebook computers.