Network Operation System. netstat. ipconfig/tracert/ping. nslookup EEE 448 Computer Networks

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1 EEE 448 Computer Networks with (Network Programming) Lecture #4 Dept of Electrical and Electronics Engineering Çukurova University Network Operation System When you are on the internet or are working in an networked environment you may think you have problems with your network connection. However it would be helpful if you could diagnose whether there is a problem and what it is. Fortunately there are some useful tools built in to all versions of Windows which can help you, you just need to know what they are and how to use them. Most of the tools on this page are accessed from the DOS or Command prompt. netstat netstat (network statistics) is a command-line tool that displays network connections for the Transmission Control Protocol (both incoming and outgoing), routing tables, a number of network interface (network interface controller or software-defined network interface), network protocol statistics. Examples netstat -a Displays all active TCP connections. And TCP / UDP ports. netstat -e Displays ethernet statistics. netstat -b Displays all active programs that are listening. getmac: Discovers the Media Access Control (MAC) address and lists associated network protocols for all network cards in a computer, either locally or across a network. Hostname : to get the computer s Hostname arp -a To get the MAC address of your router or other devices on your local network, With this information, you can find out what type of router you are connected to by using this website. S Simply plug in the MAC Address of your default gateway(found from IPCONFIG) and you can get the brand name of your router without looking at it. nslookup nslookup is a way to get the IP address for a domain name. It shows Domain Name to IP Address. It can be a way to find out if your DNS is properly working or if the site is having problems. nslookup xxx.xxx.xxx.xxx nslookup site.com ipconfig/tracert/ping to display the network settings currently assigned to any or all network adapters in the machine. İpconfig.. ipconfig /all Tracert : to visually see a network packet being sent and received and the amount of hops required for that packet to get to its destination : tracert Ping :Helps in determining TCP/IP Networks IP address as well as determine issues with the network and assists in resolving them ping

2 Namespace One of the biggest advantages is that the.net network library is the way IP address/port pairs are handled. Provides a simple programming interface to Many of the protocols found on the network today An implementation of network services that enables you to develop applications that use Internet resources.net defines two classes in the namespace to handle various types of IP address information like IPAddress IPEndPoint Primary Classes IPAddress : Provides an Internet Protocol (IP) address SocketAddress : Identifies a socket address Dns : Provides simple domain name resolution functionality DnsPermission : Controls rights to access Domain Name System (DNS) servers on the network Primary Classes (cnt.) NetworkCredential : Credentials for password-based authentication schemes HttpWebRequest, HttpWebResponse : HTTP implementation of request and response objects WebClient : Provides common methods for sending data to and receiving data from a resource identified by a URI IPAddress Method s Fields IPAddress Methods The IPAddress class also provides four read-only fields that represent special IP addresses for use in programs: Any :Used to represent any IP address available on the local system Broadcast :Used to represent the IP broadcast address for the local network Loopback : Used to represent the loopback address of the system None :Used to represent no network interface on the system Equals : Compares two IP addresses GetHashCode :Returns a hash value for an IPAddress object GetType :Returns the type of the IP address instance HostToNetworkOrder : Converts an IP address from host byte order to network byte order IsLoopBack : Indicates whether the IP address is considered the loopback address NetworkToHostOrder : Converts an IP address from network byte order to host byte order Parse : Converts a string to an IPAddress instance ToString : Converts an IPAddress to a string representation of the dotted decimal format of the IP address 2

3 using ; class AddressSample public static void Main () IPAddress test1 = IPAddress.Parse(" "); IPAddress test2 = IPAddress.Loopback; IPAddress test3 = IPAddress.Broadcast; IPAddress test4 = IPAddress.Any; IPAddress test5 = IPAddress.None; IPHostEntry ihe = Dns.GetHostByName(Dns.GetHostName()); IPAddress myself = ihe.addresslist[0]; if (IPAddress.IsLoopback(test2)) Console.WriteLine("The Loopback address is: 0", test2.tostring()); else Example Console.WriteLine("Error obtaining the loopback address"); Console.WriteLine("The Local IP address is: 0\n", myself.tostring()); if (myself == test2) Console.WriteLine("The loopback address is the as same as local address.\n"); else Console.WriteLine("The loopback address is not the local address.\n"); Console.WriteLine("The test address is: 0", test1.tostring()); Console.WriteLine("Broadcast address: 0", test3.tostring()); Console.WriteLine("The ANY address is: 0", test4.tostring()); Console.WriteLine("The NONE address is: 0", test5.tostring()); The results C:\>AddressSample The Loopback address is: The Local IP address is: The loopback address is not the local address. The test address is: Broadcast address: The ANY address is: The NONE address is: IPEndPoint the.net Framework uses the IPEndPoint object to represent a specific IP address/port combination. An IPEndPoint object is used when binding sockets to local addresses, or when connecting sockets to remote addresses. IPEndPoint Methods Create : Creates an EndPoint object from a SocketAddress object Equals : Compares two IPEndPoint objects GetHashCode : Returns a hash value for an IPEndPoint object GetType :Returns the type of the IPEndPoint instance Serialize : Creates a SocketAddress instance of the IPEndPoint instance ToString : Creates a string representation of the IPEndPoint instance Example IPEnddPoint using ; class IPEndPointSample public static void Main () IPAddress test1 = IPAddress.Parse(" "); IPEndPoint ie = new IPEndPoint(test1, 8000); Console.WriteLine("The IPEndPoint is: 0", ie.tostring()); Console.WriteLine("The AddressFamily is: 0", ie.addressfamily); Console.WriteLine("The address is: 0, and the port is: 1\n", ie.address, ie.port); Console.WriteLine("The min port number is: 0", IPEndPoint.MinPort); Console.WriteLine("The max port number is: 0\n", IPEndPoint.MaxPort); ie.port = 80; Console.WriteLine("The changed IPEndPoint value is: 0", ie.tostring()); SocketAddress sa = ie.serialize(); Console.WriteLine("The SocketAddress is: 0", sa.tostring()); The results The IPEndPoint is: :8000 The AddressFamily is: InterNetwork The address is: , and the port is: 8000 The min port number is: 0 The max port number is: The changed IPEndPoint value is: :80 The SocketAddress is: InterNetwork:16:0,80,193,140,54,11,0,0,0,0,0,0,0,0 3

4 Network Programming 1 Label 2 TextBox 1 Button using System.Text; using System.Windows.Forms; using ; namespace NetworkHostWinForms public partial class Form1 : Form public Form1() InitializeComponent(); private void button1_click(object sender, EventArgs e) try IPAddress[] ips; string hostname = Dns.GetHostName(); textbox2.clear(); ips = Dns.GetHostAddresses(textBox1.Text); foreach (IPAddress ip in ips) textbox2.appendtext(convert.tostring(ip) + Environment.NewLine); textbox2.appendtext("host Name : " + (hostname)); catch (.Sockets.SocketException ex) // Catch unknown host names MessageBox.Show(ex.Message); Definition of codes Dns.GetHostName() returns the name of the local machine and Dns.Resolve() returns IPHostEntry for a machine with a given name, the AddressList property of which returns the IPAdresses of the machine. TheResolve method will cause an exception if the mentioned host is not found. What are Sockets? Sockets provide a common interface to the various protocols supported by networks. They allow you to establish connections between machines to send and receive data. Sockets support the simultaneous connection of multiple clients to a single server machine. 21 Identify the Destination Socket Logical Structure Addressing IP address hostname (resolve to IP address via DNS) Multiplexing bytes Socket port Client socket address :3479 Server socket address :80 FTP Server (port 21) Socket bytes Client Connection socket pair ( :3479, :80) HTTP Server (port 80) Client host address Server host address

5 Well-known Ports 5