That told me that one of the fragments didn't make it. If another advertisement packet came in, then everything that had been building up was thrown away. Once all of the packets arrived, that packet got processed. I knew all the packets had arrived once the needed byte total reached zero. So, the structure was created, and the payload was simply dropped in the (correct) place in the buffer, and the bytes were subtracted from the overall total that was needed. Each packet contained a header that described what packet number it was, along with a header that told me it was part of a larger overall packet. But if I had to send a large packet, greater than 1020 bytes, I broke it up into multiple packets. If a packet got lost, it wasn't a big deal. I dealt with this issue back in 2002, in a program that was using UDP broadcasts to communicate with other running instances on the network. Even as the suggestions that I have have already been posed. IPEndPoint ep = new IPEndPoint(broadcast, 11000) Ĭonsole.This question is 12 years old, and it seems almost a waste to answer it now. IPAddress broadcast = IPAddress.Parse("192.168.1.255") īyte sendbuf = (args) Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp) Public Shared Sub Main(args() As )ĭim s As New Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp)ĭim broadcast As IPAddress = IPAddress.Parse("192.168.1.255")ĭim sendbuf As Byte() = (args(0))ĭim ep As New IPEndPoint(broadcast, 11000)Ĭonsole.WriteLine("Message sent to the broadcast address") The client sends the message string specified on the command line. The following code example uses a Socket to send UDP datagrams to the directed broadcast address 192.168.1.255, using port 11,000. Private Const listenPort As Integer = 11000ĭim listener As New UdpClient(listenPort)ĭim groupEP As New IPEndPoint(IPAddress.Any, listenPort)Ĭonsole.WriteLine("Waiting for broadcast")ĭim bytes As Byte() = listener.Receive(groupEP)Ĭonsole.WriteLine("Received broadcast from ") The client receives a message string and writes the message to the console. The following code example uses a UdpClient to listen for UDP datagrams on port 11,000. For example, to send a broadcast to all hosts on the network identified by IP addresses starting with 192.168.1, use the address 192.168.1.255. Because routers never forward messages sent to this address, only hosts on the network segment receive the broadcast message.īroadcasts can be directed to specific portions of a network by setting all bits of the host identifier. Sending a UDP datagram to this address delivers the message to any host on the local network segment. Setting all the bits of an IP address to one, or 255.255.255.255, forms the limited broadcast address. The first two octets (192.168 in this example) form the network number, the third octet (100) defines the subnet, and the final octet (2) is the host identifier. When expressed in decimal, the four octets form the familiar dotted-quad notation, such as 192.168.100.2. For class C addresses using a netmask of 255.255.255.0, these bits are separated into four octets. IP version 4 addresses use 32 bits to specify a network address. The following discussion uses the IP version 4 address family used on the Internet as an example. Special network addresses are used to support UDP broadcast messages on IP-based networks. Services not on the IANA list can have port numbers in the range 1,024 to 65,535. The Internet Assigned Numbers Authority (IANA) defines port numbers for common services (see Service Name and Transport Protocol Port Number Registry). To send a datagram using UDP, you must know the network address of the network device hosting the service you need and the UDP port number that the service uses to communicate. Applications that use UDP must be prepared to handle missing, duplicate, and out-of-sequence datagrams. However, because the UDP protocol is a connectionless protocol, UDP datagrams sent to the remote endpoint are not guaranteed to arrive, nor are they guaranteed to arrive in the same sequence in which they are sent. User Datagram Protocol (UDP) is a simple protocol that makes a best effort to deliver data to a remote host. The properties and methods of the UdpClient class abstract the details of creating a Socket for requesting and receiving data using UDP. The UdpClient class communicates with network services using UDP.
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