diff --git a/msdos/src/fn_network/network_close.c b/msdos/src/fn_network/network_close.c
index 1cec3f5..c60e6b5 100644
--- a/msdos/src/fn_network/network_close.c
+++ b/msdos/src/fn_network/network_close.c
@@ -7,5 +7,5 @@ uint8_t network_close(const char* devicespec)
 {
   uint8_t device = network_unit(devicespec) + 0x70;
 
-  return int_f5(device,'C',0x00,0x00) == 'C';
+  return int_f5(device,'C',0x00,0x00) == 'C' ? FN_ERR_OK : FN_ERR_IO_ERROR;
 }
diff --git a/msdos/src/fn_network/network_error.c b/msdos/src/fn_network/network_error.c
new file mode 100644
index 0000000..b74086b
--- /dev/null
+++ b/msdos/src/fn_network/network_error.c
@@ -0,0 +1,15 @@
+#include <stdbool.h>
+#include <stdint.h>
+#include <fujinet-network.h>
+#include <fujinet-fuji-msdos.h>
+#include <string.h>
+
+uint8_t network_error(const char *devicespec)
+{
+    uint8_t err = 0;
+    uint8_t status_ret = 0;
+
+    status_ret = network_status(devicespec, NULL, NULL, &err);
+
+    return status_ret;
+}
diff --git a/msdos/src/fn_network/network_http_set_channel_mode.c b/msdos/src/fn_network/network_http_set_channel_mode.c
index 32b06f3..e6bcd37 100644
--- a/msdos/src/fn_network/network_http_set_channel_mode.c
+++ b/msdos/src/fn_network/network_http_set_channel_mode.c
@@ -5,5 +5,5 @@
 uint8_t network_http_set_channel_mode(const char *devicespec, uint8_t mode)
 {
   uint8_t device = network_unit(devicespec) + 0x70;
-  return int_f5(device,'M',0x00,mode) == 'C';
+  return int_f5(device,'M',0x00,mode) == 'C' ? FN_ERR_OK : FN_ERR_IO_ERROR;
 }
diff --git a/msdos/src/fn_network/network_ioctl.c b/msdos/src/fn_network/network_ioctl.c
index 103df50..37c1c69 100644
--- a/msdos/src/fn_network/network_ioctl.c
+++ b/msdos/src/fn_network/network_ioctl.c
@@ -14,9 +14,9 @@ uint8_t network_ioctl(uint8_t cmd, uint8_t aux1, uint8_t aux2, const char* devic
   uint8_t *dbuf = NULL;
   uint16_t dbyt = 0;
   uint8_t ret = 0;
-  
+
   va_start(ap,devicespec);
-  
+
   if (ap)
     dstats = va_arg(ap, uint8_t);
   if (ap)
@@ -27,11 +27,11 @@ uint8_t network_ioctl(uint8_t cmd, uint8_t aux1, uint8_t aux2, const char* devic
   va_end(ap);
 
   if (dstats == 0x00)
-    ret = int_f5(device,cmd,aux1,aux2) == 'C';
+      ret = int_f5(device,cmd,aux1,aux2) == 'C' ? FN_ERR_OK : network_error(devicespec);
   else if (dstats == 0x40) // Payload to computer
-    ret = int_f5_read(device,cmd,aux1,aux2,dbuf,dbyt);
+      ret = int_f5_read(device,cmd,aux1,aux2,dbuf,dbyt) == 'C' ? FN_ERR_OK : network_error(devicespec);
   else if (dstats == 0x80) // Payload to fujinet
-    ret = int_f5_write(device,cmd,aux1,aux2,dbuf,dbyt);
-  
+      ret = int_f5_write(device,cmd,aux1,aux2,dbuf,dbyt) == 'C' ? FN_ERR_OK : network_error(devicespec);
+
   return ret;
 }
diff --git a/msdos/src/fn_network/network_json_parse.c b/msdos/src/fn_network/network_json_parse.c
index 8da5a91..b1bc553 100644
--- a/msdos/src/fn_network/network_json_parse.c
+++ b/msdos/src/fn_network/network_json_parse.c
@@ -16,5 +16,5 @@ uint8_t network_json_parse(const char *devicespec)
   // Ask FujiNet to parse JSON.
   ret = int_f5(device,'P',0x00,0x00);
 
-  return ret;
+  return ret == 'C' ? FN_ERR_OK : FN_ERR_IO_ERROR;
 }
diff --git a/msdos/src/fn_network/network_json_query.c b/msdos/src/fn_network/network_json_query.c
index 9f4f2a2..ee6db7c 100644
--- a/msdos/src/fn_network/network_json_query.c
+++ b/msdos/src/fn_network/network_json_query.c
@@ -15,7 +15,7 @@ int16_t network_json_query(const char *devicespec, const char *query, char *s)
   // Perform query
   ret = int_f5_write(device,'Q',0x00,0x00,(void *)query,256);
   if (ret != 'C')
-    return ret;
+    return -1;
 
   // Get # of bytes waiting
   network_status(devicespec,&bw,&c,&err);
@@ -33,7 +33,7 @@ int16_t network_json_query(const char *devicespec, const char *query, char *s)
       }
       s[bw - offset] = '\0';
   }
-  
+
     // return the string length (minus any trailing EOL char)
 	return bw - offset;
 }
diff --git a/msdos/src/fn_network/network_open.c b/msdos/src/fn_network/network_open.c
index 3232ff5..3a782a0 100644
--- a/msdos/src/fn_network/network_open.c
+++ b/msdos/src/fn_network/network_open.c
@@ -6,6 +6,6 @@
 uint8_t network_open(const char* devicespec, uint8_t mode, uint8_t trans)
 {
   uint8_t device = network_unit(devicespec) + 0x70;
-  
-  return int_f5_write(device,'O',mode,trans,devicespec,256);
+
+  return int_f5_write(device,'O',mode,trans,devicespec,256) == 'C' ? FN_ERR_OK : network_error(devicespec);
 }
diff --git a/msdos/src/fn_network/network_read_msdos.c b/msdos/src/fn_network/network_read_msdos.c
index c3e4b44..86685b5 100644
--- a/msdos/src/fn_network/network_read_msdos.c
+++ b/msdos/src/fn_network/network_read_msdos.c
@@ -7,5 +7,5 @@ int network_read_msdos(char* devicespec, unsigned char *buf, unsigned int len)
 {
   uint8_t device = network_unit(devicespec) + 0x70;
 
-  return int_f5_read(device,'R',len&0xFF,len>>8,(void *)buf,len) == 'C';
+  return int_f5_read(device,'R',len&0xFF,len>>8,(void *)buf,len) == 'C' ? len : FN_ERR_IO_ERROR;
 }
diff --git a/msdos/src/fn_network/network_write.c b/msdos/src/fn_network/network_write.c
index a6798b7..a8aa7cb 100644
--- a/msdos/src/fn_network/network_write.c
+++ b/msdos/src/fn_network/network_write.c
@@ -6,6 +6,6 @@
 uint8_t network_write(const char* devicespec, const uint8_t *buf, uint16_t len)
 {
   uint8_t device = network_unit(devicespec) + 0x70;
-  
-  return int_f5_write(device,'W',len&0xFF,len>>8,(void *)buf,len) == 'C';
+
+  return int_f5_write(device,'W',len&0xFF,len>>8,(void *)buf,len) == 'C' ? len : FN_ERR_IO_ERROR;
 }
diff --git a/msdos/src/include/fujinet-fuji-msdos.h b/msdos/src/include/fujinet-fuji-msdos.h
index e004e72..46d4ff7 100644
--- a/msdos/src/include/fujinet-fuji-msdos.h
+++ b/msdos/src/include/fujinet-fuji-msdos.h
@@ -17,4 +17,6 @@ unsigned char int_f5(unsigned char dev, unsigned char command, unsigned char aux
 unsigned char int_f5_read(unsigned char dev, unsigned char command, unsigned char aux1, unsigned char aux2, void *buf, unsigned short len);
 unsigned char int_f5_write(unsigned char dev, unsigned char command, unsigned char aux1, unsigned char aux2, const void *buf, unsigned short len);
 
+unsigned char network_error(const char *devicespec);
+
 #endif /* FUJINET_FUJI_MSDOS_H */