problem with costate.c sample

i’m using an example program called costate_tcp.c from volume 1 of TCP, the program compiles normally with out any error, when we run the program we can only send one data string to the socket, it detects an error and then the communication is lost.
the error it’s the next:

"Run time error: an RST38 occurred, but the RST38 vector is uninitialized. address 00:ebea

i run step by step the program and i found out that when it reaches tcp_tick(NULL) an error ocurres, we even tried changing NULL for �&mysocket