error 10170 expecting identifier ,;

i got the following errors for the code i developed

Error (10170): Verilog HDL syntax error at arbiter_for_8_clients.v(59) near text "("; expecting an identifier
Error (10170): Verilog HDL syntax error at arbiter_for_8_clients.v(59) near text ")"; expecting ";"

59 for (i= (last_served_port+1),((gnt_valid==0)&&(i<=8)),i=i+ 1)
if(port_req[i]==1) begin
gnt_port=i;
gnt_valid=1;
end

Please suggest the corrections to be made. Thanks