update

Author: JamesChung

tcp.md

@@ -0,0 +1,19 @@
+# TCP
+
+## Opening a TCP connection
+
+> With telnet
+```
+telnet <URL>:<port>
+
+# Example:
+telnet api.example.com 80
+```
+
+> With OpenSSL
+```
+openssl s_client --quiet --connect <URL>:<port>
+
+# Example:
+openssl s_client --quiet --connect api.example.com:443
+```

web.md

@@ -4,7 +4,7 @@
 
 ![URL vs URI vs URN](images/url_uri_urn.jpg)
 
-## URI
+### URI
 
 URI stands for Uniform Resource Identifier. It identifies a logical or physical resource on the web. URL and URN are subtypes of URI. URL locates a resource, while URN names a resource.
 
@@ -14,10 +14,10 @@ A URI is composed of the following parts:
 scheme:[//authority]path[?query][#fragment]
 ```
 
-## URL
+### URL
 
 URL stands for Uniform Resource Locator, the key concept of HTTP. It is the address of a unique resource on the web. It can be used with other protocols like FTP and JDBC.
 
-## URN
+### URN
 
 URN stands for Uniform Resource Name. It uses the urn scheme. URNs cannot be used to locate a resource. A simple example given in the diagram is composed of a namespace and a namespace-specific string.