Opening a file and echoing the contents from it to the file descriptor

I've been stuck on this for hours because I really don't understand file descriptors and how successfully print a file to one.


Basically, I want to be able to open a file and then echo its contents a character at a time to a socket file descriptor. The code below will hopefully help you to understand, and I've made a start on what I think is correct. I just can't figure out what to include in the while loop, although I think it is through use of char *fgets and int fputs. Any help whatsoever will be greatly appreciated.

Code:

void echoFile(int fd, char *filename) {


    // file pointer
    FILE* fp;
    
    // open 'filename' and assign the pointer
    if((fp = fopen(filename, "r")) == NULL) {
            fprintf(stderr, "The file specified does not exist\n");
    }
    
    //while loop to read each character from 'filename' to the file descriptor
    while(getc(fp) != EOF) {
  
    }
}

First you need to know what a file descriptor (sometimes called a file handle) is... CLICK

Second you need to know what a socket is (and this is where it gets complex)... CLICK

Basically you need to first open a socket, then get it connected to something... some sort of client that can absorb the data... then stream data from the file to the socket....

If this is your first week of programming and/or you haven't finished your textbook yet, I strongly suggest you do that first. Sockets programming, especially with Winsock is NOT beginner software.

Sorry I haven't been very clear here.

EDIT:
I have already created the socket in the main method, which basically results in:

Code:

int connection_sckt;
connection_sckt = accept(list_s, NULL, NULL);

//and then what I think should be...
echoFile(connection_sckt, filename)
//which would cop the contents of filename to the connection_sckt(if this is in fact the correct fd)

Have you tried getting it to work without sending the output to a socket? That might help you get your head sorted a bit.

That way, at least you'll know that you're echoing the contents properly. So from there, you can begin to attack the other problems one piece at a time.

Write down your plan of attack.

Thats not a bad idea, thanks for that! I'll get right on that now, but in the meantime am I correct if I were to go along the lines of:

Code:

voidechoFile(int fd, char*filename) {

    FILE* fp;
    FILE* fr;

    //open the file in read mode
    fp = open(filename, "r");

    //open the file in write mode
    fr = open(fd, "w");

    while(c = getc(fp) != EOF) {
        putc(c, fr)
    }
    
    fclose(fp);
    fclose(fr);

}

You will want fgetc() and fputc() for lines 12 and 13... getc() and putc() work with keyboard and screen.

Originally Posted by purpleturtle_97

Sorry I haven't been very clear here.

EDIT:
I have already created the socket in the main method, which basically results in:

Code:

int connection_sckt;
connection_sckt = accept(list_s, NULL, NULL);

//and then what I think should be...
echoFile(connection_sckt, filename)
//which would cop the contents of filename to the connection_sckt(if this is in fact the correct fd)

You should post your whole code and let us look at it.

Trust me... simply calling accept does not open a socket.
And using fput() to echo characters to the socket handle does not send data.

Here's an example of what it takes to open a listening socket in Winsock...

Code:

// initialize Client port/return port number
WORD InitNetwork(WORD Port)
  { WSADATA     wsadata;              // winsock startup
    TCHAR       hn[MAX_HOSTNAME];     // host name
    DWORD       hs = MAX_HOSTNAME;    // host name size
    SOCKADDR    la;                   // local address
    WORD        lp = Port;            // local port
    // Load the Winsock DLL
    if (WSAStartup(MAKEWORD(2,0),&wsadata))
      return 0;
    // initialize local socket
    hSocket = socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);
    if (hSocket == INVALID_SOCKET)
      return 0;
    // initialize localhost IP  
    GetComputerName(hn,&hs);
    if (!GetHostAddr(hn,Port,&la))
      return 0;
    // bind on user designated Port
    if (bind(hSocket,&la,sizeof(SOCKADDR)))
      return 0; 
    // start rx thread
    rxThread = CreateThread(NULL,0,&ReceiveDatagrams,NULL,0,0);
    return lp; }

This is for UDP connections, TCP is a little different but no less complex.