diff --git a/simulators/simic275.c b/simulators/simic275.c
index 388ddd2f7..6f4b3ccc0 100644
--- a/simulators/simic275.c
+++ b/simulators/simic275.c
@@ -103,7 +103,7 @@ again:
         }
     }
 
-    printf("Error??? c=x%02x\n", c);
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -113,6 +113,12 @@ void frameParse(int fd, unsigned char *frame, int len)
     double freq;
     int n = 0;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     dumphex(frame, len);
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
diff --git a/simulators/simic7000.c b/simulators/simic7000.c
index 388ddd2f7..6f4b3ccc0 100644
--- a/simulators/simic7000.c
+++ b/simulators/simic7000.c
@@ -103,7 +103,7 @@ again:
         }
     }
 
-    printf("Error??? c=x%02x\n", c);
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -113,6 +113,12 @@ void frameParse(int fd, unsigned char *frame, int len)
     double freq;
     int n = 0;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     dumphex(frame, len);
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
diff --git a/simulators/simic705.c b/simulators/simic705.c
index 5b270ed1a..a281ed618 100644
--- a/simulators/simic705.c
+++ b/simulators/simic705.c
@@ -94,7 +94,7 @@ again:
         }
     }
 
-    printf("Error??? c=x%02x\n", c);
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -104,6 +104,12 @@ void frameParse(int fd, unsigned char *frame, int len)
     double freq;
     int n = 0;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     dumphex(frame, len);
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
diff --git a/simulators/simic7100.c b/simulators/simic7100.c
index a7494c9be..afeae7de2 100644
--- a/simulators/simic7100.c
+++ b/simulators/simic7100.c
@@ -101,7 +101,7 @@ again:
         }
     }
 
-    printf("Error??? c=x%02x\n", c);
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -111,6 +111,12 @@ void frameParse(int fd, unsigned char *frame, int len)
     double freq;
     int n = 0;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     dumphex(frame, len);
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
diff --git a/simulators/simic7200.c b/simulators/simic7200.c
index 927df1f86..6acbcb4c1 100644
--- a/simulators/simic7200.c
+++ b/simulators/simic7200.c
@@ -115,7 +115,7 @@ again:
         }
     }
 
-    printf("Error??? c=x%02x\n", c);
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -125,6 +125,12 @@ void frameParse(int fd, unsigned char *frame, int len)
     double freq;
     int n = 0;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     dumphex(frame, len);
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
diff --git a/simulators/simic7300.c b/simulators/simic7300.c
index c74ea71fb..92f1bf481 100644
--- a/simulators/simic7300.c
+++ b/simulators/simic7300.c
@@ -96,7 +96,7 @@ again:
         }
     }
 
-    printf("Error??? c=x%02x\n", c);
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -106,6 +106,12 @@ void frameParse(int fd, unsigned char *frame, int len)
     double freq;
     int n = 0;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     dumphex(frame, len);
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
diff --git a/simulators/simic7600.c b/simulators/simic7600.c
index 2089e7085..9d625e072 100644
--- a/simulators/simic7600.c
+++ b/simulators/simic7600.c
@@ -94,7 +94,7 @@ again:
         }
     }
 
-    printf("Error??? c=x%02x\n", c);
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -104,6 +104,12 @@ void frameParse(int fd, unsigned char *frame, int len)
     double freq;
     int n = 0;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     dumphex(frame, len);
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
diff --git a/simulators/simic7610.c b/simulators/simic7610.c
index d8dd118e0..a319f6233 100644
--- a/simulators/simic7610.c
+++ b/simulators/simic7610.c
@@ -94,7 +94,7 @@ again:
         }
     }
 
-    printf("Error??? c=x%02x\n", c);
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -104,6 +104,12 @@ void frameParse(int fd, unsigned char *frame, int len)
     double freq;
     int n = 0;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     dumphex(frame, len);
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
diff --git a/simulators/simic7851.c b/simulators/simic7851.c
index 0986741fe..3c62339a6 100644
--- a/simulators/simic7851.c
+++ b/simulators/simic7851.c
@@ -69,7 +69,7 @@ frameGet(int fd, unsigned char *buf)
 {
     int i = 0;
     memset(buf, 0, BUFSIZE);
-    unsigned char c;
+    unsigned char c = 0xff;
 
 again:
 
@@ -101,7 +101,7 @@ again:
         }
     }
 
-    printf("Error??? c=x%02x\n", c);
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -111,7 +111,18 @@ void frameParse(int fd, unsigned char *frame, int len)
     double freq;
     int n = 0;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     //dumphex(frame, len);
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
     {
diff --git a/simulators/simic905.c b/simulators/simic905.c
index 9ee8ced5a..9038f09c8 100644
--- a/simulators/simic905.c
+++ b/simulators/simic905.c
@@ -99,7 +99,7 @@ again:
         }
     }
 
-    printf("Error??? c=x%02x\n", c);
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -108,6 +108,12 @@ void frameParse(int fd, unsigned char *frame, int len)
 {
     double freq;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     dumphex(frame, len);
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
diff --git a/simulators/simic9100.c b/simulators/simic9100.c
index 6ab0aeed6..afd7e1587 100644
--- a/simulators/simic9100.c
+++ b/simulators/simic9100.c
@@ -93,7 +93,7 @@ again:
         }
     }
 
-    printf("Error??? c=x%02x\n", c);
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -102,6 +102,12 @@ void frameParse(int fd, unsigned char *frame, int len)
 {
     double freq;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     dumphex(frame, len);
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
diff --git a/simulators/simic9700.c b/simulators/simic9700.c
index 96ce3c1af..9c2763e4d 100644
--- a/simulators/simic9700.c
+++ b/simulators/simic9700.c
@@ -95,7 +95,7 @@ again:
         }
     }
 
-    printf("Error??? c=x%02x\n", c);
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -104,6 +104,12 @@ void frameParse(int fd, unsigned char *frame, int len)
 {
     double freq;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     dumphex(frame, len);
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
diff --git a/simulators/simicgeneric.c b/simulators/simicgeneric.c
index 45ae53a0d..0fb95584d 100644
--- a/simulators/simicgeneric.c
+++ b/simulators/simicgeneric.c
@@ -69,7 +69,7 @@ frameGet(int fd, unsigned char *buf)
         }
     }
 
-    printf("Error???\n");
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
@@ -78,6 +78,12 @@ void frameParse(int fd, unsigned char *frame, int len)
 {
     double freq;
 
+    if (len == 0)
+    {
+        printf("%s: len==0\n", __func__);
+        return;
+    }
+
     dumphex(frame, len);
 
     if (frame[0] != 0xfe && frame[1] != 0xfe)
diff --git a/simulators/simid5100.c b/simulators/simid5100.c
index 5d270e03d..9fe31f3ec 100644
--- a/simulators/simid5100.c
+++ b/simulators/simid5100.c
@@ -90,7 +90,7 @@ again:
         }
     }
 
-    printf("Error???\n");
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }
diff --git a/simulators/simxiegug90.c b/simulators/simxiegug90.c
index ff4bd4cad..390854b03 100644
--- a/simulators/simxiegug90.c
+++ b/simulators/simxiegug90.c
@@ -69,7 +69,7 @@ frameGet(int fd, unsigned char *buf)
         }
     }
 
-    printf("Error???\n");
+    printf("Error %s\n", strerror(errno));
 
     return 0;
 }