add streaming-server with web client (#164)

* add streaming-server with web client

* small fixes

python-api-examples/web/generate-certificate.py

@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+
+"""
+pip install pyopenssl
+"""
+
+from OpenSSL import crypto
+
+# The code in this file is modified from
+# https://stackoverflow.com/questions/27164354/create-a-self-signed-x509-certificate-in-python
+
+"""
+This script generates 3 files:
+    - private.key
+    - selfsigned.crt
+    - cert.pem
+
+You need cert.pem when you start a https server
+or a secure websocket server.
+
+Note: You need to change serialNumber if you want to generate
+a new certificate as two different certificates cannot share
+the same serial number if they are issued by the same organization.
+
+Otherwise, you may get the following error from within you browser:
+
+  An error occurred during a connection to 127.0.0.1:6007. You have received an
+  invalid certificate. Please contact the server administrator or email
+  correspondent and give them the following information: Your certificate
+  contains the same serial number as another certificate issued by the
+  certificate authority. Please get a new certificate containing a unique
+  serial number. Error code: SEC_ERROR_REUSED_ISSUER_AND_SERIAL
+
+"""
+
+
+def cert_gen(
+    emailAddress="https://github.com/k2-fsa/k2",
+    commonName="sherpa",
+    countryName="CN",
+    localityName="k2-fsa",
+    stateOrProvinceName="k2-fsa",
+    organizationName="k2-fsa",
+    organizationUnitName="k2-fsa",
+    serialNumber=3,
+    validityStartInSeconds=0,
+    validityEndInSeconds=10 * 365 * 24 * 60 * 60,
+    KEY_FILE="private.key",
+    CERT_FILE="selfsigned.crt",
+    ALL_IN_ONE_FILE="cert.pem",
+):
+    # can look at generated file using openssl:
+    # openssl x509 -inform pem -in selfsigned.crt -noout -text
+    # create a key pair
+    k = crypto.PKey()
+    k.generate_key(crypto.TYPE_RSA, 4096)
+    # create a self-signed cert
+    cert = crypto.X509()
+    cert.get_subject().C = countryName
+    cert.get_subject().ST = stateOrProvinceName
+    cert.get_subject().L = localityName
+    cert.get_subject().O = organizationName  # noqa
+    cert.get_subject().OU = organizationUnitName
+    cert.get_subject().CN = commonName
+    cert.get_subject().emailAddress = emailAddress
+    cert.set_serial_number(serialNumber)
+    cert.gmtime_adj_notBefore(0)
+    cert.gmtime_adj_notAfter(validityEndInSeconds)
+    cert.set_issuer(cert.get_subject())
+    cert.set_pubkey(k)
+    cert.sign(k, "sha512")
+    with open(CERT_FILE, "wt") as f:
+        f.write(
+            crypto.dump_certificate(crypto.FILETYPE_PEM, cert).decode("utf-8")
+        )
+    with open(KEY_FILE, "wt") as f:
+        f.write(crypto.dump_privatekey(crypto.FILETYPE_PEM, k).decode("utf-8"))
+
+    with open(ALL_IN_ONE_FILE, "wt") as f:
+        f.write(crypto.dump_privatekey(crypto.FILETYPE_PEM, k).decode("utf-8"))
+        f.write(
+            crypto.dump_certificate(crypto.FILETYPE_PEM, cert).decode("utf-8")
+        )
+    print(f"Generated {CERT_FILE}")
+    print(f"Generated {KEY_FILE}")
+    print(f"Generated {ALL_IN_ONE_FILE}")
+
+
+cert_gen()