4 files changed, 27 insertions, 2 deletions

diff --git a/csim/sim.c b/csim/sim.c
index 1dd2791..4451d0e 100644
--- a/csim/sim.c
+++ b/csim/sim.c
@@ -74,6 +74,13 @@ void read_inputs(t_machine *m, FILE *stream) {
     t_id var;
     t_program *p = m->prog;
 
+    int magic;
+    fscanf(stream, " %x", &magic);
+    if (magic != 0xFEED) {
+        fprintf(stderr, "(simulator) Protocol error.\n");
+        exit(1);
+    }
+
     if (p->n_inputs == 0) return;       // nothing to do
 
     for (i = 0; i < p->n_inputs; i++) {
@@ -213,6 +220,8 @@ void write_outputs(t_machine *m, FILE *stream) {
     t_value v, mask;
     t_program *p = m->prog;
 
+    fprintf(stream, "FED\n");
+
     for (i = 0; i < p->n_outputs; i++) {
         var = p->outputs[i];
         fprintf(stream, "%s\t", p->vars[var].name);
diff --git a/monitor/main.c b/monitor/main.c
index 1de722c..ff48dcf 100644
--- a/monitor/main.c
+++ b/monitor/main.c
@@ -36,6 +36,7 @@ int main(int argc, char *argv[]) {
             fprintf(stderr, "(simulator) Could not open mon2sim for reading (%s).\n", strerror(errno));
             return 1;
         }
+        fprintf(stderr, "(simulator) Syncronization with monitor apparently OK.\n");
         execv (argv[1], argv + 1);
     }
 
@@ -55,6 +56,7 @@ int main(int argc, char *argv[]) {
         fprintf(stderr, "\nError while launching simulator (%d).\n", err);
         goto finish;
     }
+    fprintf(stderr, "(monitor) Syncronization with simulator apparently OK.\n");
 
     // Setup display
     disp_init();
@@ -65,6 +67,10 @@ int main(int argc, char *argv[]) {
     // clean up
     disp_finish();
 
+    if (mon.status == MS_PERROR) {
+        fprintf(stderr, "(monitor) Exiting due to protocol error.\n");
+    }
+
 finish:
     kill(sim_pid, SIGTERM);
     waitpid(sim_pid);
diff --git a/monitor/mon.c b/monitor/mon.c
index baef98b..780e8ba 100644
--- a/monitor/mon.c
+++ b/monitor/mon.c
@@ -82,7 +82,7 @@ void mon_loop(t_mon *mon) {
 
     int displayer_steps = 0;
 
-    while (mon->status != MS_FINISH) {
+    while (1) {
         handle_kbd(mon);
         if (mon->status == MS_AUTO) {
             mon_step(mon);
@@ -125,8 +125,10 @@ void mon_loop(t_mon *mon) {
             }
             int sleep = 1000000 / mon->target_freq - mon->calc_time_usec;
             if (sleep > 0) usleep(sleep);
-        } else {
+        } else if (mon->status == MS_RUN) {
             usleep(10000);
+        } else {
+            break;
         }
     }
 }
@@ -266,12 +268,19 @@ void mon_step(t_mon *mon) {
     }
     
     // Send inputs to simulator
+    fprintf(mon->to_sim, "FEED\n");
     for (i = 0; i < mon->n_inputs; i++) {
         fprintf(mon->to_sim, "%s\n", mon->inputs[i].value);
     }
     fflush(mon->to_sim);
 
     // Read outputs from simulator
+    int magic;
+    fscanf(mon->from_sim, " %x", &magic);
+    if (magic != 0xFED) {
+        mon->status = MS_PERROR;
+        return;
+    }
     for (i = 0; i < mon->n_outputs; i++) {
         fscanf(mon->from_sim, " %s %s %d",
             mon->outputs[i].name,
diff --git a/monitor/mon.h b/monitor/mon.h
index 32d60c4..4430e5f 100644
--- a/monitor/mon.h
+++ b/monitor/mon.h
@@ -20,6 +20,7 @@ typedef struct {
 } t_input;
 
 typedef enum {
+    MS_PERROR,
     MS_FINISH,
     MS_RUN,
     MS_AUTO,