modbuslog: flush serial IO buffers on modbus errorv1.6

1 files changed, 18 insertions, 0 deletions

diff --git a/src/modbuslog.c b/src/modbuslog.c
index cb509ea..3f9b658 100644
--- a/src/modbuslog.c
+++ b/src/modbuslog.c
@@ -44,6 +44,9 @@
 
 #include <syslog.h>
 
+#include <termios.h>
+#include <fcntl.h>
+
 // handle SIGALRM by resetting it
 void minute_check(int signum) {
 	alarm(60);
@@ -271,6 +274,21 @@ int main(int argc, char *argv[]) {
 						// back off for 2 secs, increasing by 2 for each
 						// incorrect reply
 						sleep(2+retry*2);
+
+						// open serial port file descriptor,
+						// flush IO, write zero-ouput, reflush IO,
+						// close file descriptor
+						int fd = open(modbus_device_address, O_RDWR | O_NOCTTY );
+						if (tcflush(fd, TCIOFLUSH) == 0){
+							syslog(LOG_WARNING, "Flushing [%s] serial IO buffer", modbus_device_address);
+						}
+						if (tcsendbreak(fd, 0) == 0){
+							syslog(LOG_WARNING, "Writing zero-value bits to [%s]", modbus_device_address);
+						}
+						if (tcflush(fd, TCIOFLUSH) == 0){
+							syslog(LOG_WARNING, "Reflushing [%s] serial IO buffer", modbus_device_address);
+						}
+						close(fd);
 					}
 					retry++;
 				} while ((rc == -1) && (retry <= modbus_retry));