diff --git a/src/include/lib3270.h b/src/include/lib3270.h
index 0a17703..d0bbf9c 100644
--- a/src/include/lib3270.h
+++ b/src/include/lib3270.h
@@ -1052,23 +1052,23 @@
 	/**
 	 * @brief Find the buffer address of the field attribute for a given buffer address.
 	 *
-	 * @param h		Session handle.
-	 * @param addr	Buffer address of the field.
+	 * @param hSession	Session handle.
+	 * @param addr		Buffer address of the field.
 	 *
-	 * @return field address or -1 if the screen isn't formatted.
+	 * @return field address or -1 if the screen isn't formatted (sets errno).
 	 *
 	 */
-	LIB3270_EXPORT int lib3270_field_addr(H3270 *h, int baddr);
+	LIB3270_EXPORT int lib3270_field_addr(H3270 *hSession, int baddr);
 
 	LIB3270_EXPORT int lib3270_field_attribute(H3270 *hSession, int baddr);
 
 	/**
 	 * @brief Get the length of the field at given buffer address.
 	 *
-	 * @param h		Session handle.
-	 * @param addr	Buffer address of the field.
+	 * @param hSession	Session handle.
+	 * @param addr		Buffer address of the field.
 	 *
-	 * @return field length.
+	 * @return field length or -1 if invalid or not connected (sets errno).
 	 *
 	 */
 	LIB3270_EXPORT int lib3270_field_length(H3270 *h, int baddr);
diff --git a/src/lib3270/bounds.c b/src/lib3270/bounds.c
index 41d314f..cee0372 100644
--- a/src/lib3270/bounds.c
+++ b/src/lib3270/bounds.c
@@ -34,16 +34,22 @@
 
 /*--[ Implement ]------------------------------------------------------------------------------------*/
 
-LIB3270_EXPORT int lib3270_get_field_bounds(H3270 *session, int baddr, int *start, int *end)
+/**
+ * Get field region
+ *
+ * @param hSession	Session handle.
+ * @param baddr		Reference position to get the field start/stop offsets.
+ * @param start		return location for start of selection, as a character offset.
+ * @param end		return location for end of selection, as a character offset.
+ *
+ * @return -1 if invalid or not connected (sets errno).
+ *
+ */
+LIB3270_EXPORT int lib3270_get_field_bounds(H3270 *hSession, int baddr, int *start, int *end)
 {
 	int first;
 
-	CHECK_SESSION_HANDLE(session);
-
-	if(!lib3270_connected(session))
-		return -1;
-
-	first = lib3270_field_addr(session,baddr);
+	first = lib3270_field_addr(hSession,baddr);
 
 	if(first < 0)
 		return -1;
@@ -55,8 +61,8 @@ LIB3270_EXPORT int lib3270_get_field_bounds(H3270 *session, int baddr, int *star
 
 	if(end)
 	{
-		int maxlen = (session->rows * session->cols)-1;
-		*end	= first + lib3270_field_length(session,first);
+		int maxlen = (hSession->rows * hSession->cols)-1;
+		*end	= first + lib3270_field_length(hSession,first);
 		if(*end > maxlen)
 			*end = maxlen;
 	}
diff --git a/src/lib3270/ctlr.c b/src/lib3270/ctlr.c
index db5fe10..e7b1ac5 100644
--- a/src/lib3270/ctlr.c
+++ b/src/lib3270/ctlr.c
@@ -483,6 +483,15 @@ LIB3270_EXPORT int lib3270_get_field_len(H3270 *hSession, int baddr)
 	return -1;
 }
 
+/**
+ * @brief Find the buffer address of the field attribute for a given buffer address.
+ *
+ * @param hSession	Session handle.
+ * @param addr		Buffer address of the field.
+ *
+ * @return field address or -1 if the screen isn't formatted (sets errno).
+ *
+ */
 LIB3270_EXPORT int lib3270_field_addr(H3270 *hSession, int baddr)
 {
 	int sbaddr;
@@ -503,6 +512,7 @@ LIB3270_EXPORT int lib3270_field_addr(H3270 *hSession, int baddr)
 		DEC_BA(baddr);
 	} while (baddr != sbaddr);
 
+	errno = EINVAL;
 	return -1;
 }
 
@@ -510,10 +520,13 @@ LIB3270_EXPORT int lib3270_field_attribute(H3270 *hSession, int baddr)
 {
 	int sbaddr;
 
-	CHECK_SESSION_HANDLE(hSession);
+	FAIL_IF_NOT_ONLINE(hSession);
 
-	if (!hSession->formatted)
+	if(!hSession->formatted)
+	{
+		errno = ENOTCONN;
 		return -1;
+	}
 
 	sbaddr = baddr;
 	do
@@ -523,12 +536,20 @@ LIB3270_EXPORT int lib3270_field_attribute(H3270 *hSession, int baddr)
 		DEC_BA(baddr);
 	} while (baddr != sbaddr);
 
+	errno = EINVAL;
 	return -1;
+
 }
 
 
-/*
- * Get Field width
+/**
+ * @brief Get the length of the field at given buffer address.
+ *
+ * @param hSession	Session handle.
+ * @param addr		Buffer address of the field.
+ *
+ * @return field length or -1 if invalid or not connected (sets errno).
+ *
  */
 int lib3270_field_length(H3270 *hSession, int baddr)
 {
@@ -536,8 +557,6 @@ int lib3270_field_length(H3270 *hSession, int baddr)
 	int addr;
 	int width = 0;
 
-	CHECK_SESSION_HANDLE(hSession);
-
 	addr = find_field_attribute(hSession,baddr);
 
 	if(addr < 0)
@@ -553,6 +572,7 @@ int lib3270_field_length(H3270 *hSession, int baddr)
 		width++;
 	} while (addr != saddr);
 
+	errno = EINVAL;
 	return -1;
 
 }
@@ -566,11 +586,26 @@ unsigned char get_field_attribute(H3270 *hSession, int baddr)
 	return hSession->ea_buf[find_field_attribute(hSession,baddr)].fa;
 }
 
+/**
+ * @brief Find the next unprotected field.
+ *
+ * @param hSession	Session handle.
+ * @param baddr0	Search start addr (-1 to use current cursor position).
+ *
+ * @return address following the unprotected attribute byte, or 0 if no nonzero-width unprotected field can be found, -1 if not connected.
+ *
+ */
 LIB3270_EXPORT int lib3270_get_next_unprotected(H3270 *hSession, int baddr0)
 {
 	register int baddr, nbaddr;
 
-    CHECK_SESSION_HANDLE(hSession);
+	FAIL_IF_NOT_ONLINE(hSession);
+
+	if(!hSession->formatted)
+	{
+		errno = ENOTCONN;
+		return -1;
+	}
 
 	if(baddr0 < 0)
 		baddr0 = hSession->cursor_addr;
@@ -588,13 +623,12 @@ LIB3270_EXPORT int lib3270_get_next_unprotected(H3270 *hSession, int baddr0)
 }
 
 LIB3270_EXPORT int lib3270_get_is_protected_at(H3270 *h, int row, int col) {
-	CHECK_SESSION_HANDLE(h);
 	return lib3270_get_is_protected(h, ((row-1) * h->cols) + (col-1));
 }
 
 LIB3270_EXPORT int lib3270_get_is_protected(H3270 *hSession, int baddr)
 {
-    CHECK_SESSION_HANDLE(hSession);
+	FAIL_IF_NOT_ONLINE(hSession);
 
     if(baddr < 0)
 		baddr = hSession->cursor_addr;
@@ -1163,10 +1197,8 @@ void ctlr_erase_all_unprotected(H3270 *hSession)
 	ALL_CHANGED(hSession);
 }
 
-
-
-/*
- * Process a 3270 Write command.
+/**
+ * @brief Process a 3270 Write command.
  */
 enum pds ctlr_write(H3270 *hSession, unsigned char buf[], int buflen, Boolean erase)
 {
@@ -1993,9 +2025,8 @@ enum pds ctlr_write(H3270 *hSession, unsigned char buf[], int buflen, Boolean er
 #undef ABORT_WRITEx
 #undef ABORT_WRITE
 
-/*
- * Write SSCP-LU data, which is quite a bit dumber than regular 3270
- * output.
+/**
+ * @brief Write SSCP-LU data, which is quite a bit dumber than regular 3270 output.
  */
 void ctlr_write_sscp_lu(H3270 *hSession, unsigned char buf[], int buflen)
 {
@@ -2095,7 +2126,9 @@ void ctlr_write_sscp_lu(H3270 *hSession, unsigned char buf[], int buflen)
 
 #if defined(X3270_DBCS) /*[*/
 
-/*
+/**
+ * @brief Determine the DBCS state of a buffer location strictly by looking left.
+ *
  * Determine the DBCS state of a buffer location strictly by looking left.
  * Used only to validate write operations.
  * Returns only DBCS_LEFT, DBCS_RIGHT or DBCS_NONE.
@@ -2367,7 +2400,7 @@ int ctlr_dbcs_postprocess(H3270 *hSession)
 #endif /*]*/
 
 /**
- * Process pending input.
+ * @brief Process pending input.
  *
  * @param hSession	Session handle.
  */
@@ -2464,10 +2497,8 @@ static void ctlr_blanks(H3270 *session)
 	ALL_CHANGED(session);
 }
 
-
 /**
- * Change a character in the 3270 buffer, removes any field attribute defined at that location.
- *
+ * @brief Change a character in the 3270 buffer, removes any field attribute defined at that location.
  *
  */
 void ctlr_add(H3270 *hSession, int baddr, unsigned char c, unsigned char cs)
diff --git a/src/lib3270/testprogram/testprogram.c b/src/lib3270/testprogram/testprogram.c
index 806deae..005c914 100644
--- a/src/lib3270/testprogram/testprogram.c
+++ b/src/lib3270/testprogram/testprogram.c
@@ -11,7 +11,7 @@ int main(int numpar, char *param[])
 {
 	H3270		* h;
 	int			  rc	= 0;
-	const char  * url	= getenv("TN3270URL");
+	const char  * url	= getenv("LIB3270_DEFAULT_HOST");
 
 
 	h = lib3270_session_new("");
--
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