>Hi,
>Problem was not in the writing in file. I have verified all the received packages and have discovered that some arrive filled with white spaces. Therefore, the problem is in the transmission that the Web server does to my socket. Packages always corrupt such. The IIS must badly read the file for some reason.
>
>I don´t know what to do now with this problem.
>
>Thanks.

Are the white spaces inserted throughout the block or only at the end? And what exactly is a "white space"? Is it chr(32) (space) or is it chr(0) (NULL)? If at the end, you could write logic on the receiving end to strip off the final junk characters before reassembling the file.

Do you have access to the split logic? Maybe there is a problem there. If the white spaces are scattered throughout the package then you will need to examine the split logic to determine what's going on. Maybe you could post the code if it's not too involved.