Merge pull request #2 from mbeigel/choose-port

Add option to choose port from command line

README.md

@@ -6,7 +6,10 @@ This is the source code for my post on [Building a Blockchain](https://medium.co
 
 1. Make sure [Python 3.6+](https://www.python.org/downloads/) is installed
 1. Install requirements: `$ pip install -r requirements.txt`
-1. Run the server: `$ python blockchain.py`
+1. Run the server:
+    * `$ python blockchain.py` 
+    * `$ python blockchain.py -p 5001`
+    * `$ python blockchain.py --port 5002`
 
 ## Contributing
 

blockchain.py

@@ -279,4 +279,11 @@ def consensus():
 
 
 if __name__ == '__main__':
-    app.run(host='0.0.0.0', port=5000)
+    from argparse import ArgumentParser
+
+    parser = ArgumentParser()
+    parser.add_argument('-p', '--port', default=5000, type=int, help='port to listen on')
+    args = parser.parse_args()
+    port = args.port
+
+    app.run(host='0.0.0.0', port=port)