suchithra, from your post, I can understand the problem wel, but you didn't mentioned whether you were using any wired/wireless communication. Look, I have done so many programs for interfacing, establishments of communications for different mechatronic devices etc. & faced lots of probs. The best practice would be throughing Exceptions, so that you can understand where the problem is. I rather suggest you- 1. Use UDP protocol other than using TCP/IP protocol. 2. If you are sending bulk data, then check for stack overflow 3. Try to Impliment of your own timeout block or extend socket timeout value 4. Swap your globally stored data to local veriable, so that before every recieve, your global block should be cleaned. 5. Check your h/w connection for communication. "Retransmission Timeout" error occurs: 1. It means either no data is being recieved by your VC++ aps(use Exceptions to check atallit recieve any data from sender or not) or it recieves few data, after that communication lost (cause by stack overflow/ h/w issue), which is quite obvious in TCP/IP protocol for large data transfer. Use UDP only.