TCP是面向连接的可靠的服务，需要建立连接。TCP provides a way for applications to send encapsulated IP datagrams and send them having to establish a connection
TCP是端对端的不支持多播。TCP does not support multicasting.
0-1024是专用端口。Port numbers below 1024 are called well-known ports and are reserved for standard services. For example,port 21 is reserved for FTP protocol, and port 25 is for SMTP protocol.
TCP能保证可靠服务。TCP handles package loss reliably