(FTP = File Transfer Protocol
(DRAFT: Liable to change) Aaron Sloman
School of Computer Science, University of Birmingham
Likewise transferring files between a smartphone and a computer can be messy and tedious. Some people use an internet site with file hosting services as an intermediary, e.g. Dropbox.
One way to make file manipulation less tedious is to connect a keyboard and mouse to the phone, but you will still face the limitations of using a small screen. And that will not, in itself, solve the problem of transferring files between the phone and another local machine.
This can be achieved if the phone has a wifi link to a local network to which your PC or laptop is also connected either wirelessly or using a cable connection to the router as shown in the diagram (where "wavy" lines indicate wireless connections). All traffic between machines goes through the router.
This mode of transfer through a local network is both more convenient and more private than transferring files through a "cloud storage" facility such as Dropbox or google's cloud. It can also be much faster than using a broadband internet connection.
The diagram below indicates schematically a small local wifi+cable network with three devices connected to a shared router. In principle there could be several more devices connected via cable or wirelessly. The technology used in this example is FTP which stands for "File Transfer Protocol". The standards were originally set up in the early 1970s and gradually evolved as networks became larger and more complex and additional requirements for reliability, security, efficency and increasing numbers of connected computers connected over increasing distances were added. Such details are not discussed here.
The FTP server runs on a "remote" machine whose files you wish to access. "Remote" here does not refer to distance, merely the fact that you are not interacting directly: the remote machine on which the FTP server program runs could be your smartphone physically adjacent to your PC, for example.
The machine you interact with physically, e.g. via keyboard and mouse or touchpad, is your "client" or "local" machine. So file transfer, and file manipulation using FTP requires two programs, the FTP client program running on the machine you interact with physically, and the FTP server program running on the machine you access through the local machine. (Perhaps the labels "local" and "remote" should be replaced with "direct" and "indirect".)
[Note: In principle, there could be several local clients connected in parallel, e.g. if different users are simultaneously using local machines to access the same phone (or other device running an FTP server). Likewise your local network could have more than one FTP server, e.g. if you have a shared machine used for backup, or for storing shared video and audio files.]
The "client" program on your "local" machine requests information or sends instructions about files on the remote machine by sending messages to the "server" program, which either performs actions (e.g. installing, renaming or deleting files as requested) or sends back information, e.g. about which files are available on the remote machine. The client FTP program can list the available remote files or ask for copies to be downloaded to the local machine, and deleted if required. It can also cause copies of local files to be "uploaded" to the remote machine.
E.g. if the remote machine has a camera (like many smartphones), it may have image or video files produced by the camera. So one common use of FTP is fetching image or video files to a local machine -- and possibly using FTP later on to transfer copies to another location, e.g. on a web site.
For this to work, you will have to set up an FTP Server on your phone, e.g. using the ES File Explorer App as explained below. It works very well, but I wasted a huge amount of time trying to find out how to do it. This is my attempt to help others avoid a similar waste of time.
It is also possible to use FTP to upload, download, or manipulate files on a truly remote machine, such as an external web server accessed via your internet connection, e.g. if you create and manage a web site on some remote host. In that case someone who manages the remote host will normally have to set up the FTP Server.
By communicating with the "remote" FTP server, your FTP client program on the local machine (e.g. your PC) allows you also to upload files from the PC to the phone, e.g. photos, videos, pdf documents, etc.
FTP server packages seem to differ as to which files they allow you to access on the phone. E.g. I tried one File server app with glowing reports and found that on my Moto G3 phone running Android 6, with an SD card containing photographs and video recordings I could not access the items on the SD card remotely. (The SD card had been "imported" into Android.)
ES File Explorer does not have that restriction. But after I installed the App on the phone I could not, at first, work out how to start the FTP server (see below). Once it was running, however, all the files I needed, including files on the SD card, were accessible when I was working either at my PC or my laptop machine (both running linux -- Fedora 24), and using Filezilla as my local FTP client.
But I wasted a lot of time finding out how to start the server on the phone. The online documentation I found seemed to refer to an older version of ES File Explorer, with a different interface. My version was installed in November 2016.
Eventually, after wasting a great deal of time, I found that there was a button to start the server, but its label did not mention FTP. It was labelled "View on PC"! This may be useful for someone who has never heard of FTP but it is the wrong label for someone seeking an FTP server.
The problem was made worse by the fact that the relevant button was not immediately visible when the File Explorer App started up, That's because the lower half of the screen was always covered by a (useless?) panel labelled "What is .nomedia file?". Various other things could be accessed via menus on that page, or by swiping right or left, whereas swiping down or up did nothing. So I assumed there was nothing more to find on that page.
After wasting a lot of time without success, I noticed a barely visible "v" just above the "What is .nomedia file?" panel. Tapping on that eventually revealed six more menu items, including the "View on PC" button -- the one needed to start the FTP server! However, the first time I found it I ignored it, as I thought it was intended to allow the phone user to access files on a PC (i.e. starting a ftp client).
Eventually I tried the "View on PC" button. That indicated the Wifi Router and a "Turn on" button at the bottom with some text saying "You can manage your device through your PC after you turn on the service." It should have said: "...after you start the FTP server on this phone".
When you start the server program on the phone it will also ask you to provide a user name and password that a client program will use to connect with the server. (You can decide whether to use a fixed name and password, or whether it should be changed every time you start the FTP server, which is much less convenient.)
The first time you start the FTP server it will show you an address that you will need to type into the ftp client software on the other machine (e.g. your PC). It may be something like this. ftp://192.168.0.15:3721
The first four numbers (e.g. 192.168.0.15) give the network address that has been assigned to the phone by your router. To ensure that your router always gives your phone the same address you will have to find out how to instruct the router's DHCP subsection to "reserve" an address for your phone. How to do that will depend on which router you have, and will not be explained here.
The number after the colon (in this case 3721) is the "port number" to be used by your FTP client, e.g. the FTP software running on your PC, to communicate with the FTP server running on the phone.
Different types of connections between your phone and other things will use different port numbers. Often the port number for an FTP server is 21, but the ES File Server chooses a different number, ending in 21. When you first start the FTP client on your PC (e.g. Filezilla) it will ask for the port number, so you need to have it ready. (The tutorials listed below may help you work out how to insert it in Filezilla if it's not obvious.)
Make sure you keep a record of the name and password you type in as you will need to insert both of them into the FTP client package when you start up a connection on the PC. (The client program on the PC, e.g. Filezilla, may provide you with the option to remember the user name and password. Whether it is safe to do that will depend on who else might have access to your PC when it is on the same network as the phone.)
I assume you can give the FTP server on the phone different user names and passwords for use in different contexts, e.g. in another house, but I have not tried that.
That web site also shows you how to use the connection to transfer files, after
it has started up:
It's a pity there are no good tutorials on how to use the latest version of ES File Explorer to set up an FTP server on the phone. If you find one, let me know and I'll add a link to it.
Installed: 1 Dec 2016
Last updated: 3 Dec 2016
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