diff --git a/oletools/msodde.py b/oletools/msodde.py
index fd121b2..a425513 100644
--- a/oletools/msodde.py
+++ b/oletools/msodde.py
@@ -6,7 +6,7 @@ msodde is a script to parse MS Office documents
 (e.g. Word, Excel), to detect and extract DDE links.
 
 Supported formats:
-- Word 2007+ (.docx, .dotx, .docm, .dotm)
+- Word 97-2003 (.doc, .dot), Word 2007+ (.docx, .dotx, .docm, .dotm)
 
 Author: Philippe Lagadec - http://www.decalage.info
 License: BSD, see source code or documentation
@@ -46,8 +46,10 @@ from __future__ import print_function
 # CHANGELOG:
 # 2017-10-18 v0.52 PL: - first version
 # 2017-10-20       PL: - fixed issue #202 (handling empty xml tags)
+# 2017-10-25       CH: - add json output
+# 2017-10-25       CH: - parse doc
 
-__version__ = '0.52dev2'
+__version__ = '0.52dev3'
 
 #------------------------------------------------------------------------------
 # TODO: detect beginning/end of fields, to separate each field
@@ -71,7 +73,14 @@ import argparse
 import zipfile
 import os
 import sys
+import json
 
+from oletools.thirdparty import olefile
+
+# === PYTHON 2+3 SUPPORT ======================================================
+
+if sys.version_info[0] >= 3:
+    unichr = chr
 
 # === CONSTANTS ==============================================================
 
@@ -83,23 +92,195 @@ TAG_W_INSTRTEXT = '{%s}instrText' % NS_WORD
 TAG_W_FLDSIMPLE = '{%s}fldSimple' % NS_WORD
 TAG_W_INSTRATTR= '{%s}instr' % NS_WORD
 
-# === FUNCTIONS ==============================================================
+# banner to be printed at program start
+BANNER = """msodde %s - http://decalage.info/python/oletools
+THIS IS WORK IN PROGRESS - Check updates regularly!
+Please report any issue at https://github.com/decalage2/oletools/issues
+""" % __version__
 
-def process_args():
-    parser = argparse.ArgumentParser(description='A python tool to detect and extract DDE links in MS Office files')
-    parser.add_argument("filepath", help="path of the file to be analyzed")
+BANNER_JSON = dict(type='meta', version=__version__, name='msodde',
+                   link='http://decalage.info/python/oletools',
+                   message='THIS IS WORK IN PROGRESS - Check updates regularly! '
+                            'Please report any issue at '
+                            'https://github.com/decalage2/oletools/issues')
 
-    args = parser.parse_args()
+# === ARGUMENT PARSING =======================================================
 
-    if not os.path.exists(args.filepath):
-        print('File {} does not exist.'.format(args.filepath))
-        sys.exit(1)
+class ArgParserWithBanner(argparse.ArgumentParser):
+    """ Print banner before showing any error """
+    def error(self, message):
+        print(BANNER)
+        super(ArgParserWithBanner, self).error(message)
 
-    return args
 
+def existing_file(filename):
+    """ called by argument parser to see whether given file exists """
+    if not os.path.exists(filename):
+        raise argparse.ArgumentTypeError('File {0} does not exist.'
+                                         .format(filename))
+    return filename
 
 
-def process_file(filepath):
+def process_args(cmd_line_args=None):
+    parser = ArgParserWithBanner(description='A python tool to detect and extract DDE links in MS Office files')
+    parser.add_argument("filepath", help="path of the file to be analyzed",
+                        type=existing_file, metavar='FILE')
+    parser.add_argument("--json", '-j', action='store_true',
+                        help="Output in json format")
+
+    return parser.parse_args(cmd_line_args)
+
+
+# === FUNCTIONS ==============================================================
+
+# from [MS-DOC], section 2.8.25 (PlcFld):
+# A field consists of two parts: field instructions and, optionally, a result. All fields MUST begin with
+# Unicode character 0x0013 with sprmCFSpec applied with a value of 1. This is the field begin
+# character. All fields MUST end with a Unicode character 0x0015 with sprmCFSpec applied with a value
+# of 1. This is the field end character. If the field has a result, then there MUST be a Unicode character
+# 0x0014 with sprmCFSpec applied with a value of 1 somewhere between the field begin character and
+# the field end character. This is the field separator. The field result is the content between the field
+# separator and the field end character. The field instructions are the content between the field begin
+# character and the field separator, if one is present, or between the field begin character and the field
+# end character if no separator is present. The field begin character, field end character, and field
+# separator are collectively referred to as field characters.
+
+
+def process_ole_field(data):
+    """ check if field instructions start with DDE
+
+    expects unicode input, returns unicode output (empty if not dde) """
+    #print('processing field \'{0}\''.format(data))
+
+    if data.lstrip().lower().startswith(u'dde'):
+        #print('--> is DDE!')
+        return data
+    else:
+        return u''
+
+
+OLE_FIELD_START = 0x13
+OLE_FIELD_SEP = 0x14
+OLE_FIELD_END = 0x15
+OLE_FIELD_MAX_SIZE = 1000   # max field size to analyze, rest is ignored
+
+
+def process_ole_stream(stream):
+    """ find dde links in single ole stream
+
+    since ole file stream are subclasses of io.BytesIO, they are buffered, so
+    reading char-wise is not that bad performanc-wise """
+
+    have_start = False
+    have_sep = False
+    field_contents = None
+    result_parts = []
+    max_size_exceeded = False
+    idx = -1
+    while True:
+        idx += 1
+        char = stream.read(1)    # loop over every single byte
+        if len(char) == 0:
+            break
+        else:
+            char = ord(char)
+
+        if char == OLE_FIELD_START:
+            #print('DEBUG: have start at {}'.format(idx))
+            #if have_start:
+            #    print("DEBUG: dismissing previous contents of length {}"
+            #          .format(len(field_contents)))
+            have_start = True
+            have_sep = False
+            max_size_exceeded = False
+            field_contents = u''
+            continue
+        elif not have_start:
+            continue
+
+        # now we are after start char but not at end yet
+        if char == OLE_FIELD_SEP:
+            #print('DEBUG: have sep at {}'.format(idx))
+            have_sep = True
+        elif char == OLE_FIELD_END:
+            #print('DEBUG: have end at {}'.format(idx))
+
+            # have complete field now, process it
+            result_parts.append(process_ole_field(field_contents))
+
+            # re-set variables for next field
+            have_start = False
+            have_sep = False
+            field_contents = None
+        elif not have_sep:
+            # check that array does not get too long by accident
+            if max_size_exceeded:
+                pass
+            elif len(field_contents) > OLE_FIELD_MAX_SIZE:
+                #print('DEBUG: exceeded max size')
+                max_size_exceeded = True
+
+            # appending a raw byte to a unicode string here. Not clean but
+            # all we do later is check for the ascii-sequence 'DDE' later...
+            elif char < 128:
+                field_contents += unichr(char)
+                #print('DEBUG: at idx {:4d}: add byte {} ({})'
+                #      .format(idx, unichr(char), char))
+            else:
+                field_contents += u'?'
+                #print('DEBUG: at idx {:4d}: add byte ? ({})'
+                #      .format(idx, char))
+    #print('\nstream len = {}'.format(idx))
+
+    # copy behaviour of process_xml: Just concatenate unicode strings
+    return u''.join(result_parts)
+
+
+def process_ole_storage(ole):
+    """ process a "directory" inside an ole stream """
+    results = []
+    for st in ole.listdir(streams=True, storages=True):
+        st_type = ole.get_type(st)
+        if st_type == olefile.STGTY_STREAM:      # a stream
+            stream = None
+            links = ''
+            try:
+                stream = ole.openstream(st)
+                #print('Checking stream {0}'.format(st))
+                links = process_ole_stream(stream)
+            except:
+                raise
+            finally:
+                if stream:
+                    stream.close()
+            if links:
+                results.append(links)
+        elif st_type == olefile.STGTY_STORAGE:   # a storage
+            #print('Checking storage {0}'.format(st))
+            links = process_ole_storage(st)
+            if links:
+                results.extend(links)
+        else:
+            #print('Warning: unexpected type {0} for entry {1}. Ignore it'
+            #      .format(st_type, st))
+            continue
+    return results
+
+
+def process_ole(filepath):
+    """ find dde links in ole file
+
+    like process_xml, returns a concatenated unicode string of dde links or
+    empty if none were found. dde-links will still being with the dde[auto] key
+    word (possibly after some whitespace)
+    """
+    #print('Looks like ole')
+    ole = olefile.OleFileIO(filepath, path_encoding=None)
+    text_parts = process_ole_storage(ole)
+    return u'\n'.join(text_parts)
+
+
+def process_xml(filepath):
     z = zipfile.ZipFile(filepath)
     data = z.read('word/document.xml')
     z.close()
@@ -117,26 +298,63 @@ def process_file(filepath):
         # concatenate the attribute of the field, if present:
         if elem.attrib is not None:
             text += elem.attrib[TAG_W_INSTRATTR]
-    
 
     return text
 
 
-#=== MAIN =================================================================
+def process_file(filepath):
+    """ decides to either call process_xml or process_ole """
+    if olefile.isOleFile(filepath):
+        return process_ole(filepath)
+    else:
+        return process_xml(filepath)
+
 
-def main():
-    # print banner with version
-    print ('msodde %s - http://decalage.info/python/oletools' % __version__)
-    print ('THIS IS WORK IN PROGRESS - Check updates regularly!')
-    print ('Please report any issue at https://github.com/decalage2/oletools/issues')
-    print ('')
+#=== MAIN =================================================================
 
-    args = process_args()
-    print('Opening file: %s' % args.filepath)
-    text = process_file(args.filepath)
-    print ('DDE Links:')
-    print(text)
+def main(cmd_line_args=None):
+    """ Main function, called if this file is called as a script
+
+    Optional argument: command line arguments to be forwarded to ArgumentParser
+    in process_args. Per default (cmd_line_args=None), sys.argv is used. Option
+    mainly added for unit-testing
+    """
+    args = process_args(cmd_line_args)
+
+    if args.json:
+        jout = []
+        jout.append(BANNER_JSON)
+    else:
+        # print banner with version
+        print(BANNER)
+
+    if not args.json:
+        print('Opening file: %s' % args.filepath)
+
+    text = ''
+    return_code = 1
+    try:
+        text = process_file(args.filepath)
+        return_code = 0
+    except Exception as exc:
+        if args.json:
+            jout.append(dict(type='error', error=type(exc).__name__,
+                             message=str(exc)))  # strange: str(exc) is enclosed in ""
+        else:
+            raise
+
+    if args.json:
+        for line in text.splitlines():
+            jout.append(dict(type='dde-link', link=line.strip()))
+        json.dump(jout, sys.stdout, check_circular=False, indent=4)
+        print()   # add a newline after closing "]"
+        return return_code  # required if we catch an exception in json-mode
+    else:
+        print ('DDE Links:')
+        print(text)
+
+    return return_code
 
 
 if __name__ == '__main__':
-    main()
+    sys.exit(main())
diff --git a/tests/howto_add_unittests.txt b/tests/howto_add_unittests.txt
new file mode 100644
index 0000000..3178741
--- /dev/null
+++ b/tests/howto_add_unittests.txt
@@ -0,0 +1,37 @@
+Howto: Add unittests
+--------------------
+
+For helping python's unittest to discover your tests, do the
+following:
+
+* create a subdirectory within oletools/tests/
+  - The directory name must be a valid python package name,
+    so must not include '-', for example
+  - e.g. oletools/tests/my_feature
+
+* Create a __init__.py inside that directory
+  - can be empty but must be there
+
+* Copy the unittest_template.py into your test directory
+
+* Rename your copy of the template to fit its purpose
+  - file name must start with 'test' and end with '.py'
+  - e.g. oletools/tests/my_feature/test_bla.py
+
+* Create python code inside that directory
+  - classes names must start with Test and must be subclasses
+    of Unittest.TestCase
+  - test functions inside your test cases must start with test_
+  - see unittest_template.py for examples
+
+* If your unit test requires test files, put them into a subdir
+  of oletools/tests/test-data with some name that clarifies what
+  tests it belongs to
+  - e.g. oletools/tests/test-data/my_feature/example.doc
+  - Do not add files with actual evil malware macros! Only harmless
+    test data!
+
+* Test that unittests work by running from the oletools base dir:
+  python -m unittest discover -v
+
+* Re-test with python2 and python3 (if possible)
diff --git a/tests/msodde_doc/__init__.py b/tests/msodde_doc/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tests/msodde_doc/__init__.py
diff --git a/tests/msodde_doc/test_basic.py b/tests/msodde_doc/test_basic.py
new file mode 100644
index 0000000..0d366b1
--- /dev/null
+++ b/tests/msodde_doc/test_basic.py
@@ -0,0 +1,119 @@
+""" Test some basic behaviour of msodde.py
+
+Ensure that
+- doc and docx are read without error
+- garbage returns error return status
+- dde-links are found where appropriate
+"""
+
+from __future__ import print_function
+
+import unittest
+from oletools import msodde
+import shlex
+from os.path import join, dirname, normpath
+import sys
+
+# python 2/3 version conflict:
+if sys.version_info.major <= 2:
+    from StringIO import StringIO
+    #from io import BytesIO as StringIO - try if print() gives UnicodeError
+else:
+    from io import StringIO
+
+
+# base directory for test input
+BASE_DIR = normpath(join(dirname(__file__), '..', 'test-data'))
+
+
+class TestReturnCode(unittest.TestCase):
+
+    def test_valid_doc(self):
+        """ check that a valid doc file leads to 0 exit status """
+        print(join(BASE_DIR, 'msodde-doc/test_document.doc'))
+        self.do_test_validity(join(BASE_DIR, 'msodde-doc/test_document.doc'))
+
+    def test_valid_docx(self):
+        """ check that a valid docx file leads to 0 exit status """
+        self.do_test_validity(join(BASE_DIR, 'msodde-doc/test_document.docx'))
+
+    def test_invalid_none(self):
+        """ check that no file argument leads to non-zero exit status """
+        self.do_test_validity('', True)
+
+    def test_invalid_empty(self):
+        """ check that empty file argument leads to non-zero exit status """
+        self.do_test_validity(join(BASE_DIR, 'basic/empty'), True)
+
+    def test_invalid_text(self):
+        """ check that text file argument leads to non-zero exit status """
+        self.do_test_validity(join(BASE_DIR, 'basic/text'), True)
+
+    def do_test_validity(self, args, expect_error=False):
+        """ helper for test_valid_doc[x] """
+        args = shlex.split(args)
+        return_code = -1
+        have_exception = False
+        try:
+            return_code = msodde.main(args)
+        except Exception:
+            have_exception = True
+        except SystemExit as se:     # sys.exit() was called
+            return_code = se.code
+            if se.code is None:
+                return_code = 0
+
+        self.assertEqual(expect_error, have_exception or (return_code != 0))
+
+
+class OutputCapture:
+    """ context manager that captures stdout """
+
+    def __init__(self):
+        self.output = StringIO()   # in py2, this actually is BytesIO
+
+    def __enter__(self):
+        sys.stdout = self.output
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        sys.stdout = sys.__stdout__    # re-set to original
+
+        if exc_type:   # there has been an error
+            print('Got error during output capture!')
+            print('Print captured output and re-raise:')
+            for line in self.output.getvalue().splitlines():
+                print(line.rstrip())  # print output before re-raising
+
+    def __iter__(self):
+        for line in self.output.getvalue().splitlines():
+            yield line.rstrip()   # remove newline at end of line
+
+
+class TestDdeInDoc(unittest.TestCase):
+
+    def test_with_dde(self):
+        """ check that dde links appear on stdout """
+        with OutputCapture() as capturer:
+            msodde.main([join(BASE_DIR, 'msodde-doc', 'dde-test.doc')])
+
+        for line in capturer:
+            print(line)
+            pass    # we just want to get the last line
+
+        self.assertNotEqual(len(line.strip()), 0)
+
+    def test_no_dde(self):
+        """ check that no dde links appear on stdout """
+        with OutputCapture() as capturer:
+            msodde.main([join(BASE_DIR, 'msodde-doc', 'test_document.doc')])
+
+        for line in capturer:
+            print(line)
+            pass    # we just want to get the last line
+
+        self.assertEqual(line.strip(), '')
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/tests/test-data/basic/empty b/tests/test-data/basic/empty
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tests/test-data/basic/empty
diff --git a/tests/test-data/basic/text b/tests/test-data/basic/text
new file mode 100644
index 0000000..a7f8d9e
--- /dev/null
+++ b/tests/test-data/basic/text
@@ -0,0 +1 @@
+bla
diff --git a/tests/test-data/msodde-doc/dde-test.doc b/tests/test-data/msodde-doc/dde-test.doc
new file mode 100644
index 0000000..da5562c
--- /dev/null
+++ b/tests/test-data/msodde-doc/dde-test.doc
diff --git a/tests/test-data/msodde-doc/test_document.doc b/tests/test-data/msodde-doc/test_document.doc
new file mode 100644
index 0000000..2c1768f
--- /dev/null
+++ b/tests/test-data/msodde-doc/test_document.doc
diff --git a/tests/test-data/msodde-doc/test_document.docx b/tests/test-data/msodde-doc/test_document.docx
new file mode 100644
index 0000000..4dd2265
--- /dev/null
+++ b/tests/test-data/msodde-doc/test_document.docx
diff --git a/tests/unittest_template.py b/tests/unittest_template.py
new file mode 100644
index 0000000..a5c2cb6
--- /dev/null
+++ b/tests/unittest_template.py
@@ -0,0 +1,37 @@
+""" Test my new feature
+
+Some more info if you want
+
+Should work with python2 and python3!
+"""
+
+import unittest
+
+# if you need data from oletools/test-data/DIR/, uncomment these lines:
+#from os.path import join, dirname, normpath
+#Directory with test data, independent of current working directory
+#DATA_DIR = normpath(join(dirname(__file__), '..', 'test-data', 'DIR'))
+
+
+class TestMyFeature(unittest.TestCase):
+    """ Tests my cool new feature """
+
+    def test_this(self):
+        """ check that this works """
+        pass   # your code here
+
+    def test_that(self):
+        """ check that that also works """
+        pass   # your code here
+
+    def helper_function(self, filename):
+        """ to be called from other test functions to avoid copy-and-paste
+
+        this is not called by unittest directly, only from your functions """
+        pass   # your code here
+        # e.g.: msodde.main(join(DATA_DIR, filename))
+
+
+# just in case somebody calls this file as a script
+if __name__ == '__main__':
+    unittest.main()