rename gpio.c to gpiod.c for it will conflict with rpi gpio command

guowenxue

2021-11-03 f696e95a01ee103605a9ed5fd23de58847ab9abc

 apue/2.Socket/socket_client.c

@@ -109,7 +109,8 @@
          }
       }

       //printf("Read %d bytes data from server: '%s'\n", rv, buf);

       sleep(5);
    }