 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
.NET Forum / Languages / Managed C++ / July 2005Peculiar Error in Network Transmission
Hi, I am trying to transfer data from a Unix machine to Windows machine using C Network functions. In unix i send image data to windows using send() function in a loop running till the end of image data (length is known beforehand). sending 1022 bytes at a time when i send binary image data, i use recv command in windows to get data 1022 bytes at a time.it works fine. But when i try to send JPEG image data. Only the first 4 bytes of JPEG header (FF D8 FF E0) are received. the rest of the 1018 bytes are not received, in the next send(), transmission starts from 1023 bytes after the start of image data, from this point on data is transmitted and received correctly. I have observed that if Image data has consecutive zeros - 00 i.e 0x30 0x30. Data is either not read by recv() or transmitted by send() [i actually dont know which command is at fault since both return 1022 bytes data read/written]. Any help will be greatly appreciated. thanks and regards Actually i figured out the problem, I am using a String Array to write data from Image file and am using this String Array to transmit data using Send(). The 00 is a NULL character in C and when encountered in the array C thinks the Array has ended. But the JPEG image data i want to transfer contains a lot of NULL characters (viewed using Hex editor), and i want to transfer the data through the network. How can I use a BYTE Array in C? Any suggestions? > Hi, > I am trying to transfer data from a Unix machine to Windows machine [quoted text clipped - 19 lines] > > thanks and regards Are you using Winsock? Or some higher level wrapper library? If you are using Winsock, the 3rd parameter to send() is the length in bytes of the byte array (2nd parameter).  SignatureRegards, Nish [VC++ MVP] http://www.voidnish.com http://blog.voidnish.com > Actually i figured out the problem, I am using a String Array to write > data [quoted text clipped - 36 lines] >> >> thanks and regards Hi Nishanth, I am using Winsock on the windows side for recv(). Actually the send() command is in the unix side. I do give the Length of the array (1022 bytes). but the problem is that there is a null character at the 5th position of the array. There are a lot of null characters in the image data stored in the array. Since NULL is the end of string in C, i am facing problems sending the whole image data. > Are you using Winsock? Or some higher level wrapper library? > [quoted text clipped - 41 lines] > >> > >> thanks and regards You are trying to use null-terminated strings to store binary data. That's your basic problem. Instead use a char array [but do not use any string manipulation functions on it] or use a void* instead. And then use the Buffer-Manipulation Routines like memcpy, memcmp etc. SignatureRegards, Nish [VC++ MVP] http://www.voidnish.com http://blog.voidnish.com > Hi Nishanth, > I am using Winsock on the windows side for recv(). [quoted text clipped - 58 lines] >> >> >> >> thanks and regards Hi Nishant, Actually I am storing (binary) Image data which i obtain from an imaging device in a Char Array. The Image data already has lots of null characters as part of image data, so when i copy into a char array it automatically becomes a null terminated string. and when i try to transmit the Char array i face problems. > You are trying to use null-terminated strings to store binary data. That's > your basic problem. [quoted text clipped - 65 lines] > >> >> > >> >> thanks and regards
Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
|
Reply to this Message
|
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.