Pascal语言实现UDP服务器设计详解 (udp服务器设计 pascal)
UDP（User Datagram Protocol）是一种无连接的数据报传输协议，它与TCP（Tranission Control Protocol）协议一起构成了Internet传输层协议。UDP协议具有简单、快速、无连接等特点，适用于传输较为简单、实时性要求较高的数据。
本文将介绍如何使用Pascal语言实现UDP服务器。在此之前，请确保您已经具备一定的Pascal编程知识和UDP协议基础。
一、UDP服务器工作原理
UDP服务器是基于UDP协议实现的一种服务端程序，它的主要作用是监听UDP端口并接收客户端发送的数据报文。传输结束后，服务器返回处理结果。
UDP服务器的工作原理如下：
1. 服务器通过指定UDP端口（通常使用1024以上的端口），开始监听UDP数据报文的到来。
2. 客户端向服务器发送UDP数据报文，报文数据包括目标IP地址和目标端口号。
3. 服务器监听到数据报文后，提取数据内容，并对数据进行处理。
4. 处理完成后，服务器向客户端发送响应数据，包括源IP地址和源端口号。
二、Pascal语言实现UDP服务器的步骤
1. 创建UDP服务器
我们需要创建一个UDP服务器来监听客户端的请求。在Pascal语言中，可以使用Socket函数库实现。
procedure createServer;
var
serverSocket: TSocket;
serverAddr: TSockAddrIn;
begin
serverSocket:= Socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
serverAddr.sin_family:= AF_INET;
serverAddr.sin_port:= htons(8888);
serverAddr.sin_addr.S_addr:= INADDR_ANY;
Bind(serverSocket, serverAddr, SizeOf(serverAddr));
end;
以上代码中，我们使用Socket函数创建一个套接字(serverSocket)，使用Bind函数将服务器套接字(serverSocket)绑定到UDP端口(8888)上。同时，我们将本地IP地址(INADDR_ANY)赋给serverAddr.sin_addr.S_addr以允许任何远程IP地址连接到该服务器。
2. 监听客户端请求
接下来，我们需要使用服务器套接字(serverSocket)监听客户端的请求。
procedure listenForRequest;
var
recvbuf: array[0..511] of char;
clientAddr: TSockAddrIn;
addrLen: integer;
bytesSent: integer;
bytesRecv: integer;
begin
addrLen:= SizeOf(clientAddr);
FillChar(clientAddr, SizeOf(clientAddr), 0);
repeat
FillChar(recvbuf, SizeOf(recvbuf), 0);
bytesRecv:= recvfrom(serverSocket, recvbuf, SizeOf(recvbuf), 0, clientAddr, addrLen);
if bytesRecv = SOCKET_ERROR then
begin
ShowMessage(‘recvfrom fled’);
Break;
end
else
begin
//处理接收到的数据recvbuf
bytesSent:= sendto(serverSocket, recvbuf, bytesRecv, 0, clientAddr, addrLen);
if bytesSent = SOCKET_ERROR then
begin
ShowMessage(‘sendto fled’);
Break;
end;
end;
until False;
end;
以上代码中，我们使用recvfrom函数监听客户端的请求，并将接收到的数据储存在recvbuf中。同时，我们使用sendto函数向客户端发送数据(recvbuf)作为响应。注意，我们在recvfrom和sendto函数中，都传入了客户端的地址clientAddr和地址长度addrLen。
3. 关闭UDP服务器套接字
当UDP服务端不再需要接收客户端请求时，我们需要关闭套接字。
procedure closeServer;
begin
CloseSocket(serverSocket);
end;
三、
本文介绍了如何使用Pascal语言实现UDP服务器。通过创建服务器、监听客户端请求和关闭UDP服务器套接字这三个步骤，我们可以成功的构建一个简单的UDP服务器。
在实际开发中，UDP服务器仅作为一个数据中转站，不具备数据包确认、数据包重传等功能，因此在数据传输可靠性和数据安全性方面，需要特别注意。
由于UDP与TCP具有不同的优缺点，因此在选择协议时，需要根据具体的应用场景进行选择，以便实现更好的数据传输效果。
相关问题拓展阅读：
linux c语言实现，udp协议
你去看下linux应用程序编程，就有UDP/TCP的编程。 你这个列子是最基础的。
UDP协议全称是用颤搜袜户数据报协议，在网络中它与TCP协议一样用于处理数据包漏缺，是一种无连接的茄激协议。在OSI模型中，在第四层–传输层，处于IP协议的上一层。UDP有不提供数据包分组、组装和不能对数据包进行排序的缺点，也就是说，当报文发送之后，是无法得知其是否安全完整到达的。UDP用来支持那些需要在计算机之间传输数据的网络应用。包括网络视频会议系统在内的众多的客户/服务器模式的网络应用都需要使用UDP协议。UDP协议从问世至今已经被使用了很多年，虽然其最初的光彩已经被一些类似协议所掩盖，但是即使是在今天UDP仍然不失为一项非常实用和可行的网络传输层协议。
c#之UDP协议的异步通信怎么做
UDP服务器：
using System;
using System.Text;
using System.Net;
using System.Net.Sockets;
namespace ConsoleUdpServer
{
class Program
{
static void Main(string args)
{
Socket socket = new Socket(AddressFamily.InterNetwork,
SocketType.Dgram,
ProtocolType.Udp);
EndPoint localEP = new IPEndPoint(IPAddress.Parse(“127.0.0.1”), 8002);
socket.Bind(localEP);
//启动异步接收
State state = new State(socket);
socket.BeginReceiveFrom(
state.Buffer, 0, state.Buffer.Length,
SocketFlags.None,
信键ref state.RemoteEP,
EndReceiveFromCallback,
state);
Console.ReadLine();
socket.Close();
}
//异步接收回调函数
static void EndReceiveFromCallback(IAsyncResult iar)
{
State state = iar.AsyncState as State;
Socket socket = state.Socket;
try
{
//完成接收
int byteRead = socket.EndReceiveFrom(iar, ref state.RemoteEP);
//显示客户端地址和端口
Console.WriteLine(“客户端终结点：{0}”, state.RemoteEP.ToString());
//显示接收信息
Console.WriteLine(“接收数据字节数：{0}”, byteRead);
string message = Encoding.Default.GetString(state.Buffer, 0, byteRead);
Console.WriteLine(“来着客户端信息：{0}”, message);
//向客户端发送信息
SendMeaage(socket, state.RemoteEP, “成功接收！”);
}
catch (Exception e)
{
Console.WriteLine(“发生异常！异常信息：”);
Console.WriteLine(e.Message);
}
finally
{
//非常重要：继续异步接收
socket.BeginReceiveFrom(
state.Buffer, 0, state.Buffer.Length,
SocketFlags.None,
ref state.RemoteEP,
EndReceiveFromCallback,
state);
}
}
///
/// 向客户端发送信息
///
/// 本地Socket（服务器Socket）
/// 客户端终结点烂坦拦
/// 信息
static void SendMeaage(Socket socket, EndPoint remoteEndPoint, string Message)
{
byte bytes = Encoding.Default.GetBytes(Message);
socket.SendTo(bytes, remoteEndPoint);
}
}
///
/// 用于异步接收处理的辅助类
///
class State
{
public State(Socket socket)
{
this.Buffer = new byte;
饥胡this.Socket = socket;
this.RemoteEP = new IPEndPoint(IPAddress.Any, 0);
}
///
/// 获取本机（服务器）Socket
///
public Socket Socket { get; private set; }
///
/// 获取接收缓冲区
///
public byte Buffer { get; private set; }
///
/// 获取/设置客户端终结点
///
public EndPoint RemoteEP;
}
}
UDP客户端
using System;
using System.Text;
using System.Net;
using System.Net.Sockets;
namespace ConsoleUdpClient
{
class Program
{
static void Main(string args)
{
Socket socket = new Socket(AddressFamily.InterNetwork,
SocketType.Dgram,
ProtocolType.Udp);
//客户端使用的终结点
EndPoint localEP = new IPEndPoint(IPAddress.Any, 0);
socket.Bind(localEP);
//启动异步接收
State state = new State(socket);
socket.BeginReceiveFrom(
state.Buffer, 0, state.Buffer.Length,
SocketFlags.None,
ref state.RemoteEP,
EndReceiveFromCallback,
state);
//向服务器发送信息
EndPoint remoteEP = new IPEndPoint(IPAddress.Parse(“127.0.0.1”), 8002);
SendMeaage(socket, remoteEP, “你好，这里是客户端，收到请回复！Over~~~~”);
Console.ReadLine();
socket.Close();
}
//异步接收回调函数
static void EndReceiveFromCallback(IAsyncResult iar)
{
State state = iar.AsyncState as State;
Socket socket = state.Socket;
try
{
//完成接收
int byteRead = socket.EndReceiveFrom(iar, ref state.RemoteEP);
//显示服务器地址和端口
Console.WriteLine(“服务器终结点：{0}”, state.RemoteEP.ToString());
//显示接收信息
Console.WriteLine(“接收数据字节数：{0}”, byteRead);
string message = Encoding.Default.GetString(state.Buffer, 0, byteRead);
Console.WriteLine(“来着服务器的信息：{0}”, message);
}
catch (Exception e)
{
Console.WriteLine(“发生异常！异常信息：”);
Console.WriteLine(e.Message);
}
finally
{
//非常重要：继续异步接收
socket.BeginReceiveFrom(
state.Buffer, 0, state.Buffer.Length,
SocketFlags.None,
ref state.RemoteEP,
EndReceiveFromCallback,
state);
}
}
///
/// 向服务器发送信息
///
/// 本地Socket
/// 服务器终结点
/// 信息
static void SendMeaage(Socket socket, EndPoint remoteEndPoint, string Message)
{
byte bytes = Encoding.Default.GetBytes(Message);
socket.SendTo(bytes, remoteEndPoint);
}
}
///
/// 用于异步接收处理的辅助类
///
class State
{
public State(Socket socket)
{
this.Buffer = new byte;
this.Socket = socket;
this.RemoteEP = new IPEndPoint(IPAddress.Any, 0);
}
///
/// 获取本机Socket
///
public Socket Socket { get; private set; }
///
/// 获取接收缓冲区
///
public byte Buffer { get; private set; }
///
/// 获取/设置客户端终结点
///
public EndPoint RemoteEP;
}
}
服务器端代码：
using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Threading;
namespace AsyncServer
{
// 定义 UdpState类
public class UdpState
{
public UdpClient udpClient;
public IPEndPoint ipEndPoint;
public const int BufferSize = 1024;
public byte buffer = new byte;
public int counter = 0;
}
// 异步UDP类
public class AsyncUdpSever
{
// 定义节贺陪点
private IPEndPoint ipEndPoint = null;
private IPEndPoint remoteEP = null;
// 定义UDP发送和接收
private UdpClient udpReceive = null;
private UdpClient udpSend = null;
//团拍正 定义端口
private const int listenPort = 1100;
private const int remotePort = 1101;
UdpState udpReceiveState = null;
UdpState udpSendState = null;
// 异步状态同步
private ManualResetEvent sendDone = new ManualResetEvent(false);
private ManualResetEvent receiveDone = new ManualResetEvent(false);
public AsyncUdpSever()
{
// 本机节点
ipEndPoint = new IPEndPoint(IPAddress.Any, listenPort);
// 远程节点
remoteEP = new IPEndPoint(Dns.GetHostAddresses(Dns.GetHostName()), remotePort);
// 实塌悔例化
udpReceive = new UdpClient(ipEndPoint);
udpSend = new UdpClient();
// 分别实例化udpSendState、udpReceiveState
udpReceiveState = new UdpState();
udpReceiveState.udpClient = udpReceive;
udpReceiveState.ipEndPoint = ipEndPoint;
udpSendState = new UdpState();
udpSendState.udpClient = udpSend;
udpSendState.ipEndPoint = remoteEP;
}
public void ReceiveMsg()
{
Console.WriteLine(“listening for messages”);
while (true)
{
lock (this)
{
// 调用接收回调函数
IAsyncResult iar = udpReceive.BeginReceive(new AsyncCallback(ReceiveCallback), udpReceiveState);
receiveDone.WaitOne();
Thread.Sleep(100);
}
}
}
// 接收回调函数
private void ReceiveCallback(IAsyncResult iar)
{
UdpState udpReceiveState = iar.AsyncState as UdpState;
if (iar.IsCompleted)
{
Byte receiveBytes = udpReceiveState.udpClient.EndReceive(iar, ref udpReceiveState.ipEndPoint);
string receiveString = Encoding.ASCII.GetString(receiveBytes);
Console.WriteLine(“Received: {0}”, receiveString);
//Thread.Sleep(100);
receiveDone.Set();
SendMsg();
}
}
// 发送函数
private void SendMsg()
{
udpSend.Connect(udpSendState.ipEndPoint);
udpSendState.udpClient = udpSend;
udpSendState.counter++;
string message = string.Format(“第{0}个UDP请求处理完成！”, udpSendState.counter);
Byte sendBytes = Encoding.Unicode.GetBytes(message);
udpSend.BeginSend(sendBytes, sendBytes.Length, new AsyncCallback(SendCallback), udpSendState);
sendDone.WaitOne();
}
// 发送回调函数
private void SendCallback(IAsyncResult iar)
{
UdpState udpState = iar.AsyncState as UdpState;
Console.WriteLine(“第{0}个请求处理完毕！”, udpState.counter);
Console.WriteLine(“number of bytes sent: {0}”, udpState.udpClient.EndSend(iar));
sendDone.Set();
}
// 主函数
public static void Main()
{
AsyncUdpSever aus = new AsyncUdpSever();
Thread t = new Thread(new ThreadStart(aus.ReceiveMsg));
t.Start();
Console.Read();
}
}
}
客户端代码：
using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Threading;
namespace AsyncClient
{
// 定义 UdpState类
public class UdpState
{
public UdpClient udpClient = null;
public IPEndPoint ipEndPoint = null;
public const int BufferSize = 1024;
public byte buffer = new byte;
public int counter = 0;
}
// 异步UDP类
public class AsyncUdpClient
{
public static bool messageSent = false;
// Receive a message and write it to the console.
// 定义端口
private const int listenPort = 1101;
private const int remotePort = 1100;
// 定义节点
private IPEndPoint localEP = null;
private IPEndPoint remoteEP = null;
// 定义UDP发送和接收
private UdpClient udpReceive = null;
private UdpClient udpSend = null;
private UdpState udpSendState = null;
private UdpState udpReceiveState = null;
private int counter = 0;
// 异步状态同步
private ManualResetEvent sendDone = new ManualResetEvent(false);
private ManualResetEvent receiveDone = new ManualResetEvent(false);
// 定义套接字
//private Socket receiveSocket;
//private Socket sendSocket;
public AsyncUdpClient()
{
// 本机节点
localEP = new IPEndPoint(IPAddress.Any, listenPort);
// 远程节点
remoteEP = new IPEndPoint(Dns.GetHostAddresses(Dns.GetHostName()), remotePort);
// 实例化
udpReceive = new UdpClient(localEP);
udpSend = new UdpClient();
// 分别实例化udpSendState、udpReceiveState
udpSendState = new UdpState();
udpSendState.ipEndPoint = remoteEP;
udpSendState.udpClient = udpSend;
udpReceiveState = new UdpState();
udpReceiveState.ipEndPoint = remoteEP;
udpReceiveState.udpClient = udpReceive;
//receiveSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
//receiveSocket.Bind(localEP);
//sendSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
//sendSocket.Bind(remoteEP);
}
// 发送函数
public void SendMsg()
{
udpSend.Connect(remoteEP);
//Thread t = new Thread(new ThreadStart(ReceiveMessages));
//t.Start();
Byte sendBytes;
string message;
while (true)
{
message = “Client” + (counter++).ToString();
lock (this)
{
sendBytes = Encoding.ASCII.GetBytes(message);
udpSendState.counter = counter;
// 调用发送回调函数
udpSend.BeginSend(sendBytes, sendBytes.Length, new AsyncCallback(SendCallback), udpSendState);
sendDone.WaitOne();
Thread.Sleep(200);
ReceiveMessages();
}
}
}
// 发送回调函数
public void SendCallback(IAsyncResult iar)
{
UdpState udpState = iar.AsyncState as UdpState;
if (iar.IsCompleted)
{
Console.WriteLine(“第{0}个发送完毕！”, udpState.counter);
Console.WriteLine(“number of bytes sent: {0}”, udpState.udpClient.EndSend(iar));
//if (udpState.counter == 10)
//{
// udpState.udpClient.Close();
//}
sendDone.Set();
}
}
// 接收函数
public void ReceiveMessages()
{
lock (this)
{
udpReceive.BeginReceive(new AsyncCallback(ReceiveCallback), udpReceiveState);
receiveDone.WaitOne();
Thread.Sleep(100);
}
}
// 接收回调函数
public void ReceiveCallback(IAsyncResult iar)
{
UdpState udpState = iar.AsyncState as UdpState;
if (iar.IsCompleted)
{
Byte receiveBytes = udpState.udpClient.EndReceive(iar, ref udpReceiveState.ipEndPoint);
string receiveString = Encoding.Unicode.GetString(receiveBytes);
Console.WriteLine(“Received: {0}”, receiveString);
receiveDone.Set();
}
}
// 主函数
public static void Main()
{
AsyncUdpClient auc = new AsyncUdpClient();
auc.SendMsg();
Console.Read();
}
}
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