Networking Programming

Networking programming 2 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM Chapter’s Objectives 1. Connecting to a Server 2. Implementing Servers 3. Sending Email 4. URL Connection 5. Advanced Socket Programming 6. UDP 3 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM Connecting to a Server  Using Telnet program.  Ex : telnet time-A.timefreq.bldrdoc.gov 13 4 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM TCP/IP Overview (1)  IP: Internet Protocol :  IP is a protocol for connecting networks  IP is a packet-based protocol  Packets can be dropped, garbled or re-ordered and duplicated:  IP promises nothing but best-effort delivery  IP usually runs over ethernet, but not always 5 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM TCP/IP Overview (2)  Addressing :  Every packet has a source and a destination  A Host is identified by an IP address.  IP addresses are 4 bytes  Example: 129.123.12.43  An IP can belong to only one host in the Internet  Routers use the IP addresses to decide where to direct packets 6 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM TCP/IP Overview (3)  TCP :  TCP is a stream-based protocol over IP  TCP promises a reliable transport  TCP takes care of packet ordering, packet loss and data corruption.  A TCP stream is a connection. 7 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM TCP/IP Overview (4) TCP over IP IP Header Src Dst IP Data TCP Header Type: TCP TCP Data Src Port Dst Port Seq Num Application Data 8 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM TCP/IP Overview (5)  TCP Connections :  A TCP connection is between a Client Host and a Server Host  The Server is passive; It just waits  The Client is active  More than one connection is allowed between to hosts  TCP connections are 4-tuples  {<src-host,src-port>,<dst-host,dst-port>} 9 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM TCP/IP Overview (6) Internet Reference Model Application Layer (HTTP, FTP, DNS, etc.) Transport Layer (TCP, UDP) Network Layer (IP) Link and Physical Layer 10 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM Ports (1)  A computer usually has one physical connection to the network. So all the data from the the network comes through this connection.  If all the data comes through the same interface how does the computer redirect to specific applications?  Recall, with IP network addresses  The computer is identified by its 32-bit IP address  The port address is used to identify the specific program or application to send the packet to. [...]... Hải-Khoa CNTT- 20 Advanced Socket Programming( 1)  Socket Timeout :  The read methods will block until data is available    Socket s = new Socket( .); s.setSoTimeout(10000); // time out after 10 seconds In JDK1.4, we can uses direct as follow  Socket s=new Socket();  s.connect(new InetSocketAddress(host, port), timeout); Create by Võ Văn Hải-Khoa CNTT- 21 Advanced Socket Programming( 2)  Half-close... CNTT- 12 Implementing Servers (1) Socket:   The Java interface with a TCP connection is a socket  A socket is a Java object which has methods to connect, accept connections and transfer data  Core Networking is in java.net.*  TCP Sockets come in two flavours: ServerSocket and Socket Create by Võ Văn Hải-Khoa CNTT- 13 Implementing Servers (2)  java.net.Socket  Socket(InetAddress address, int port)... writer.flush(); socket.shutdownOutput(); // now socket is half closed // read response data String line; while ((line = reader.readLine()) != null) 23 Võ socket.close(); Văn Hải-Khoa CNTT- Advanced Socket Programming( 3)  java.net.InetAddress :  static InetAddress getByName(String name)  returns the address for “name” Throws UnknownHostException if it’s unknown  This class is the interface from Java . 12 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM Port (3)  Somes well-know port 20 : FTP ( Data) 21 : FTP (Control) 23 : Telnet 80 : HTTP 139 : NETBIOS 13 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM Implementing. 129.1 23. 12. 43  An IP can belong to only one host in the Internet  Routers use the IP addresses to decide where to direct packets 6 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM TCP/IP Overview (3)  TCP. Networking programming 2 Create by Võ Văn Hải-Khoa CNTT- ĐHCN Tp.HCM Chapter’s Objectives 1. Connecting to a Server 2. Implementing Servers 3. Sending Email 4. URL Connection 5.