Transceiver.cpp: properly zero-terminate received commands

Previously it was assumed that a sender should zero-terminate
each command being sent. Otherwise, this could cause to printing
garbage. Let's do this manually, using the length of received
data as a position for '\0'.

Change-Id: I69f413f33156c38a853efc5a8cdc66fbfb0ca6af
diff --git a/Transceiver52M/Transceiver.cpp b/Transceiver52M/Transceiver.cpp
index 7dc4c1c..8f41c5e 100644
--- a/Transceiver52M/Transceiver.cpp
+++ b/Transceiver52M/Transceiver.cpp
@@ -661,20 +661,20 @@
 
 void Transceiver::driveControl(size_t chan)
 {
-  // check control socket
-  char buffer[MAX_PACKET_LENGTH];
-  int msgLen = -1;
-  buffer[0] = '\0';
+  char buffer[MAX_PACKET_LENGTH + 1];
+  char response[MAX_PACKET_LENGTH + 1];
+  int msgLen;
 
-  msgLen = mCtrlSockets[chan]->read(buffer, sizeof(buffer));
-
-  if (msgLen < 1) {
+  /* Attempt to read from control socket */
+  msgLen = mCtrlSockets[chan]->read(buffer, MAX_PACKET_LENGTH);
+  if (msgLen < 1)
     return;
-  }
+
+  /* Zero-terminate received string */
+  buffer[msgLen] = '\0';
 
   char cmdcheck[4];
   char command[MAX_PACKET_LENGTH];
-  char response[MAX_PACKET_LENGTH];
 
   sscanf(buffer,"%3s %s",cmdcheck,command);