Trying to write a fairly simple program that reads line by line a file from an ftp server, stores each line in a string, then writes that string to a local file on my drive. Now this is fairly easy and worked perfectly.
This is the part that gets tricky. Every time the ORIGINAL file on the ftp gets updated (a new line is added), I want that line to be added into my LOCAL file created earlier. I do NOT want to recopy the whole file contents if the files are different. I simply want to add the missing lines.
Is there any way this can be done ? Any tips will be appreciated. You don't have to submit a code. Let me know of how this can be done logically and I will try to write the code for it.
Regards
You can't read a file "line by line" from an FTP server via FTP itself.
FTP is short for File Transfer Protocol, which is for transferring files. There's no way to do anything else via that protocol. If you want to access it "line by line", you're going to have to use something other than FTP.
Related
I am working on vb.net application where I wanted to create and read a file. File will have specific extension for ex. .abcb the way I want my application to work is:
can create a file with .abcd extension
should read .abcd files only(and also application created files only so altered extension shouldn't be working)
.abcd files should show some garbage data when open in any other application(ex. word, notepad any image viewer etc.)
Now my application does 1,2(partly) step, i.e. it creates a file and load data also, it reads .abcd files only(not the altered files)
but created file can be read by other software's also.I tried searching a lot but have not found anything and don't know where to start.
Any help is appreciated!
if you don't want other programs to be able to read the content of your file then your going to have to mask it in some way, which is usually done with encryption.
assuming your not too worried about the key being compromised, the easiest way to accomplish this would be to generate a key with something like System.Security.Cryptography and use that key to encyrpt everything you send to the file and everything you read from it.
as for making your own file extension, you can make the extension of a file whatever you want when you make it:
Dim fs As FileStream = File.Create("/path/to/file/filename" & ".abcd")
the only thing that the extension does is tell the OS what progam to use when opening a file by default, which will probably be notepad since your making your own extension
We have a process in place built on Excel VBA that uploads a file to FTP Server. On the other side, our client downloads it. Very randomly, they complain that the file they received is blank (the file name is the same though). We then check at our end and see that the file that was uploaded was never blank. So here comes the problem: we're always arguing whether it was our error or theirs.
I figured that there might be a couple of reasons behind it but I have a few questions to ask before coming to conclusions:
If, say, the file was never uploaded (a possibility), what happens when the client runs a download process at their end? Can that download process generate a blank file with the same name as our output file? It sounds impossible to me but since the client is following up on this issue, I have to ask this silly question.
How does the mechanism work - what are the steps that happen on FTP server the moment my process completes uploading the file? I sometimes see that as soon as I upload the file, a 0kb file is created and then a second later (or less) the file with right size appears? Could it be possible that their process is running right before this actual file creation?
Thank you in advance for your help!
I have been given a program that uploades pdf files to an ftp server, which is something I never did. I've been asked what the behavior regarding attempting to upload a duplicate filename is. It apparently doesnt check for duplicate filenames manually, but the comand that uploads the file is My.Computer.Network.UploadFile and I can't find what happens when attempting to upload a duplicate file anywhere, does it throw an exception or overwrites the file?
It looks like My.Computer.Network.UploadFile is a wrapper around WebClient.UploadFile, and the documentation for that states:
This method uses the STOR command to upload an FTP resource.
In the FTP RFC 959 it says (I highlighted the relevant part):
STORE (STOR)
This command causes the server-DTP to accept the data
transferred via the data connection and to store the data as
a file at the server site. If the file specified in the
pathname exists at the server site, then its contents shall
be replaced by the data being transferred. A new file is
created at the server site if the file specified in the
pathname does not already exist.
So, if everything is following standards (and that part of RFC 959 hasn't been replaced, I didn't dig further!), then it should replace the existing file. However, it is possible for the server to deny overwriting of existing files, so the behavior is not guaranteed.
Of course, the best thing to do would be to try it out in your environment and see what it does.
Source code: vb.net
We are using File.Move() method to move the file from source to destination locaion.
But the destination location is being monitored by one tool, whenever we are moving files to the destination location, it will pick up the file and process it. The issue here when we try to move huge volume file like around 5GB file, the tool is immediately picking up the file and try to process it before the move operation is complete and send failure notice to all the users.. After again successfully moving the file completely, it picks up the same and process it sucessfully this time and send successful notice this time.
We can't have control over the tool which is monitoring the destination folder because it is a third party tool. However we want to find out the alternative option to place a lock over the destination foler like ReadWrite access till the move operation completes so that 3rd party will not be able to pick up or try to access that file.
Pls help us.
Not sure if it works, but you might be able to make the following work with directories as well:
FileOpen(1, "c:\file.ext", OpenMode.Binary)
Lock(1)
'Do something with file here
Unlock(1)
FileClose(1)
Reference and example here
I hope it helps.
First, I agree with #hometoast, sometimes tools like this just look for specific file extensions so you can copy in with a different file extension and then rename.
But barring that, download the file to a temp location and then Move the file into the dir getting watched. A Move does not recopy the file contents but just updates its pointers in the filesystem. Should be atomic.
I want to upload a file to a ftp server programmatically (C++). If the connection is lost while uploading a file, I wouldn't want to upload the file from scratch, but to upload only the part that I haven't sent.
Does the APPE command fulfill my demand? What list of FTP commands should I use exactly? And how?
I am googling details about APPE FTP command, what actually it does but most site just state only append. Then I try out the command to make sure it behave as expected.
I designing FTP auto sender that is used to send a log file from a machine to a server for reporting. I only want to send the last line of the log file.
When using a APPE command, it actually append the whole file content and append to the existing one in the server. This will cause the line entry duplicated.
The answer:
To do the resume of file if the last transfer is failed, there is no such command for that, but we need to use a sequence of command to achieve it.
The key point here is seek your local file to the last uploaded byte if you are using APPE command or using command REST. REST will start transfer on that particular byte start position. I end-up with this solution to perform after connection established:
Use APPE (I got the idea from FileZilla log):
Use SIZE to check for file exist and use it as resume marker.
Open local file system and seek on the marker.
Use APPE to upload and FTP server will append it automatically.
Use STOR with REST (I got the idea from edtFTPnet):
Use SIZE to check for file exist and use it as resume marker.
Send REST with the result you get from SIZE to tell FTP server to start write on the position.
Open local file system and seek on the marker.
Use STOR as normal upload.
Note that not all FTP server support for both way. I see FileZilla switch this two way depending on the server. My observation shows that using REST is the standard way. Download can also use REST to start download on the given byte position.
Remember that using resume support for ASCII transfer type will produce unexpected result since Unix and Windows have different line break byte count.
Try to manipulate FileZilla to see the behave in the log.
You can also check this useful open source FTP for .NET library on how they do it.
edtFTPnet
Check the RFC and specifically the APPEND command:
This
command causes the server-DTP to
accept the data transferred via the
data connection and to store the data
in a file at the server site. If the
file specified in the pathname exists
at the server site, then the data
shall be appended to that file;
otherwise the file specified in the
pathname shall be created at the
server site.
Note that you cannot simply APPEND the same file again. You should send the bytes remaining. That is, continue at the same position when the connection was lost.