网络协议体系(二)
1.体系结构简介
计算机之间通信分为很多种,有文件通信,web通信等,需要一套协议体系来规定通信的各种各样的规则,以保证各种各样的通信
有条不行的进行.
OSI的七层协议概念清楚,但并不实用,而现实中TCP/IP协议采用四层,而我们学习的时候才用折中的的方法,采用五层的体系结
构 如下图.
2.用wireshark截取SNMP协议在各层的报文
1.应用层
2.运输层
3.网络层
4.数据链路层
3.五层协议介绍
1.应用层
例子1 应用层HTTP协议
实验1.用telnet模拟http请求
实验2.用socket模拟http请求
using System; using System.Collections.Generic; using System.Text; using System.Net.Sockets; using System.Net; namespace SocketTest { class Program { private static Socket ConnectSocket(string server, int port) { Socket s = null; IPHostEntry hostEntry = null; // Get host related information. hostEntry = Dns.GetHostEntry(server); // Loop through the AddressList to obtain the supported AddressFamily. This is to avoid // an exception that occurs when the host IP Address is not compatible with the address family // (typical in the IPv6 case). foreach (IPAddress address in hostEntry.AddressList) { IPEndPoint ipe = new IPEndPoint(address, port); Socket tempSocket = new Socket(ipe.AddressFamily, SocketType.Stream, ProtocolType.Tcp); tempSocket.Connect(ipe); if (tempSocket.Connected) { s = tempSocket; break; } else { continue; } } return s; } // This method requests the home page content for the specified server. private static string SocketSendReceive(string server, int port) { string request = "GET /btim3.0sp1/login.aspx HTTP/1.1\r\nHost: " + server + "\r\nConnection: Close\r\nAccept-Language:zh-cn\r\nAccept-Charset:utf-8\r\nAccept-Charset:iso-8859-1,gb2312\r\n\r\n"; Byte[] bytesSent = Encoding.ASCII.GetBytes(request); Byte[] bytesReceived = new Byte[256]; // Create a socket connection with the specified server and port. Socket s = ConnectSocket(server, port); if (s == null) return ("Connection failed"); // Send request to the server. s.Send(bytesSent, bytesSent.Length, 0); // Receive the server home page content. int bytes = 0; string page = "Default HTML page on " + server + ":\r\n"; // The following will block until te page is transmitted. do { bytes = s.Receive(bytesReceived, bytesReceived.Length, 0); page = page + Encoding.ASCII.GetString(bytesReceived, 0, bytes); } while (bytes > 0); return page; } public static void Main(string[] args) { string host; int port = 88; if (args.Length == 0) // If no server name is passed as argument to this program, // use the current host name as the default. host = Dns.GetHostName(); else host = args[0]; string result = SocketSendReceive(host, port); Console.WriteLine(result); Console.Read(); } } }
2.运输层
当运输层从IP层收到UDP数据报时,就根据首部中的目的端口,把UDP数据报通过相应的端口,
上交最后的终点--应用进程
3.IP层
网络层体系结构如下:
IP数据包格式:
4.数据链路层
数据链路层报文格式:
5.物理层
备注:本文的图片全部来自与谢希仁的<<网络原理>>,在此感谢,另只是学习交流用。