Winsock file transfer

Hi!

I'm working on a simple project - I want to transfer binary files using winsock. But I've reached a major problem.

I've studied this and googled for a couple of hours, but I do NOT understand what the problem is.

int recvDll(SOCKET s)

{

    int file_size;

    char fileLength[50] = "";

    FILE *fp;

    int bytes_recieved, bytes_sent, bytes_written;

    

    int recs = recv(s, fileLength, 32, 0);

    fileLength[recs] = '\0';

    file_size = atoi(fileLength);

    

    fp = fopen("testrecv.dll", "wb");

    

    printf("[+] Size of recieved DLL: %d\n", file_size);


    while(file_size > 0)

    {

                    printf("filesize: %d\n", file_size);

                    char buf[512];

                    if(file_size >= 512)

                    {

                           bytes_recieved = recv(s, buf, 512, 0);

                    } else {

                           printf("x: %d\n", file_size);

                           bytes_recieved = recv(s, buf, file_size, 0);

                           buf[file_size] = '\0';

                           

                    }

                    fwrite(buf, bytes_recieved, 1, fp);

                    file_size -= bytes_recieved;

    }


    fclose(fp);

    return 0;

}

The server that sends the file is written i VB, and splits up the file á 512 byte. But the transfer seems to be discontinued right in the middle of the download.

This is a typical output:

[+] Size of recieved DLL: 122861

filesize: 122861

filesize: 122349

filesize: 121863

filesize: 121351

filesize: 120839

filesize: 120327

filesize: 120324

filesize: 119812

filesize: 119300

filesize: 118864

filesize: 118785

filesize: 118273

filesize: 117761

filesize: 117249

filesize: 117246

filesize: 116734

filesize: 116222

filesize: 115786

filesize: 115707

filesize: 115195

filesize: 114683

filesize: 114171

filesize: 114168

filesize: 113656

filesize: 113144

filesize: 112632

filesize: 112629

filesize: 112117

filesize: 111605

filesize: 111093

filesize: 111090

filesize: 110579

I would appreciate any help, since this has been bugging me for a long time now.

int recvDll( SOCKET socket ) { int bytes; int index; int length; char buffer[ 0x0200 ]; FILE* pFile; memset( buffer, 0, 0x0200 ); bytes = 0; bytes = ::recv( socket, buffer, 0x20, 0 ); if ( 0 == bytes ) { // closed gracefully // ... return 0; } // if if ( SOCKET_ERROR == bytes ) { // socket error // ... return 0; } // if buffer[ bytes ] = '\0'; length = 0; length = ::atoi( buffer ); if ( 0 == length ) { // atoi failed to convert the size // ... return false; } // if // receiving length this way is kinda sloppy imo // if you there isnt always 32bytes reserved for // the length string. better way would be to just // write 4byte integer in beginning of the packet // and memcpy / cast that. memset( buffer, 0, 0x0200 ); pFile = 0; pFile = ::fopen( "testrecv.dll", "wb" ); if ( 0 == pFile ) { // failed to open the file // ... return 0; } // if for ( index = 0; index <= length; ) { bytes = 0; bytes = ::recv( socket, buffer, 0x0200, 0 ); if ( 0 == bytes ) { // closed gracefully // ... ::fclose( pFile ); return 0; } // if if ( SOCKET_ERROR == bytes ) { // socket error // ... ::fclose( pFile ); return 0; } // if ::fwrite( buffer, 1, bytes, pFile ); index += bytes; } // for if ( index > length ) { // deal with trailing bytes // ie. fill the extra written // data with zeroes. // ... } // if ::fclose( pFile ); return 0; }