Hi,
i'm trying to make a client-server program using sockets (unix), that allow users to transfer files from client to server.
Im using fopen and fread/fwrite to transfer the files.
The problem is, as i don't know what kind of files the user will transfer, i have no way of knowing how to fopen the files to send!!
- if i open files in binary mode, i won't be able to send .txt files
- if i open files in text mode, i won't be able to send images and other files!!
any solution??
What makes you think that?Originally Posted by xixonga
Mainframe assembler programmer by trade. C coder when I can.
When in doubt... open in binary.
Well, the problem with text files is that they contain non-character "control codes" which can be interpreted differently, depending on the convention being used. Fortunately, most programs these days can understand all of the most common variants, so it really isn't much of an issue anymore. In other words, send everything in binary and let the recipient figure out how to open it...
Code:#include <cmath> #include <complex> bool euler_flip(bool value) { return std::pow ( std::complex<float>(std::exp(1.0)), std::complex<float>(0, 1) * std::complex<float>(std::atan(1.0) *(1 << (value + 2))) ).real() < 0; }
hi all, thanks for your replies.Well, the problem with text files is that they contain non-character "control codes" which can be interpreted differently, depending on the convention being used. Fortunately, most programs these days can understand all of the most common variants, so it really isn't much of an issue anymore. In other words, send everything in binary and let the recipient figure out how to open it...
But that's what i'am doing:
Client side:
- fopen( binary-read mode) file; fread file; sendto server
Server side:
- fopen(binary-write mode) file; recv from client chunks of data; fwrite to created file
and it sucessfully creates every file...but some file (the text ones) i can't open them. my OS (ubuntu) doesn't recognize the ascii text
Then you'll need to either (1) use a text editor/viewer that supports the DOS text format, or else (2) use a file conversion utility to convert DOS text files to your "native" format.
Code:#include <cmath> #include <complex> bool euler_flip(bool value) { return std::pow ( std::complex<float>(std::exp(1.0)), std::complex<float>(0, 1) * std::complex<float>(std::atan(1.0) *(1 << (value + 2))) ).real() < 0; }
i can't use any addtional software...i want this to be a client-server transmission service... i can't guarantee that the other computer has the specific software to read this kind of files...
Well, I guess you are going to have to ask the user to tell you what kind of files he is transferring if you don't like any of our ideas.
Mainframe assembler programmer by trade. C coder when I can.
there must be a way of knowing if some random file is binary or not!
like p2p programs...when youre exchanging files...the program must know what type of files you are transfering...otherwise the receiveir might get an unreadable document...
If you have people uploading files and other people downloading them, you have plain no way to make sure everyone gets compatible files. It's just not a problem the server should try to handle.
Files should be marked with extensions... .txt .exe .zip etc... by the uploader.
It's not your problem.
but the uploading file is marked with extensions...here's the uploading code:
client (uploader)
Code:FILE* fp = fopen(buffer,"rb"); // buffer = "server.txt" printf("uploading...\n"); while(!feof(fp)){ bzero(buffer,150); fread(buffer,sizeof(char),150,fp); send(sockfd,buffer,150,0); if (n < 0) error("ERROR writing to socket"); } write(sockfd,"quit",150); fclose(fp);
server (receiver)
Code:FILE* fp = fopen(buffer,"wb"); // buffer contains the name sent by client: "server.txt" while(1){ // bzero(buffer,150); recv(sock,buffer,150,0); if(strcmp(buffer,"quit")==0) { break; } fwrite(buffer,1,150,fp); } fclose(fp);
after this...i get a "server.txt" on server directory but i can't open it due to "character codifying" issues
Ok... can you open it in a hex editor? (They'll open anything)
Is the file size correct?
It sounds like you've got some kind of file corruption going on.
Linux editors should know how to open a .txt file...
feof() isn't your most reliable exit strategy here....
The problem is that the last fread() is not guaranteed to return 150 bytes. If you sent 150 bytes every time, you end up sending garbage at the end of your files. You need the means to couple read size with send size... Your best exit is not EOF, but when send() returns < 1 which will happen if it sends nothing or an error occurs .Code:while(!feof(fp)){ bzero(buffer,150); fread(buffer,sizeof(char),150,fp); send(sockfd,buffer,150,0); if (n < 0) error("ERROR writing to socket"); } // try this int sbytes; do { sbytes = send(sockfd,buffer, fread(buffer,sizeof(char),150,fp), 0); } while (sbytes > 0);
hm didn't noticed but yeah, the receiver files aren't the same size as the sender files....
i tried your code, and it didn't work...but i don't understand whats the problem :S
even if i am sending garbage on the last chunk of data...the .txt files should be readable!
this is odd.....
should i try to use the "open" function instead of "fopen"?
You've got to get a look at the content of those files...
For all you know at this point you are sending garbage or the problem could be on the receiver end...
i have just now used an hexadecimal reader to look inside the receiver's txt file...and it has the text content...
the only difference from the original file is that in the end...it has a bunch of dots...but i'm guessing thats because i'm sendind chunks larger than the original file...
