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();
}
}
}
View Code
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。