Solution implemented in Python3

devoff2.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python3
+
+import json
+import math
+import itertools
+from http.server import HTTPServer, BaseHTTPRequestHandler
+
+def encode(limit, data):
+    matrix = [data[x:x+limit] for x in range(0, len(data), limit)]
+
+    # fill incomplete rows
+    for i in range(len(matrix)):
+        if len(matrix[i]) < limit:
+            matrix[i] += ' '*(limit-len(matrix[i]))
+
+    transposed = zip(*matrix)
+    return ''.join(itertools.chain(*transposed))
+
+def decode(limit, data):
+    rows = math.ceil(len(data)/limit)
+    matrix = [data[x:x+rows] for x in range(0, len(data), rows)]
+    transposed = zip(*matrix)
+    return ''.join(itertools.chain(*transposed)).strip()
+
+class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
+    def do_POST(self):
+        if self.path in ('/encode', '/decode'):
+            self.handler()
+        else:
+            self.send_error(404)
+
+    def handler(self):
+        content_length = int(self.headers['Content-Length'])
+        body = self.rfile.read(content_length)
+        message = json.loads(body.decode('utf-8'))
+
+        transform = globals().get(self.path[1:])
+        data = transform(message['vueltas'], message['mensaje'])
+
+        self.send_response(200)
+        self.end_headers()        
+        self.wfile.write(json.dumps({'message': data}).encode('utf-8'))
+
+PORT = 8000
+httpd = HTTPServer(('', PORT), SimpleHTTPRequestHandler)
+print ('Server Listening at: http://{}:{}'.format(httpd.server_name, httpd.server_port))
+httpd.serve_forever()