We have a board supporting TCP/IP suite. ftp server couldn't be connected twice and hung ftp client. But telnet server works well. Additionally there are two channel in this board. Only channel II has this problem. Now I have mixed information because I trace code and TCP task received second connect passive message but valid field in TCP struct is NULL and result in connect. That's an old board, RTOS no support now,and no efficient debug method. so process is very slow.