thank u EvilSOB
i follow ur advice and do these things:
the device send variable by "Serial.print(1000+speedCount);" 10 times a second.(speedCount is an int form 0 to 9.)

and i was trying to read a long-integer :
var tmp;
...//open Serial and other code.
long tmp_long=0;
port_read_number(portSerial,&tmp_long);
tmp = tmp_long;
and i got tmp=-1036239 .is there anything i mis-understanding?

or i have to send serial 4-byte long-integer in the format "1,0,0,0"-"1,0,0,9"?