Question

C# TcpClient客户端连接服务端

已知服务端ip(本机ip)和端口
ip:172.18.9.114
portNum:51888

客户端用： client = new TcpClient(ip, portNum);无法连接成功！
但是如果改为： client = new TcpClient(Dns.GetHostName(), portNum);却能连接成功！
ip为本机ip,客户端和服务端均在本机测试，为什么我用本机ip代替Dns.GetHostName()两者无法连接啊！求前辈指教，初学者谢谢大家！

Answer 1

服务端：
class mTcpServer
{
class server
{
/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main(string[] args)
{
Thread newThread;
try
{
serverTcpListener = new TcpListener(localAddr, port);
serverTcpListener.Start();
while (true)
{
Console.Write("Waiting for a connection... ");
client = serverTcpListener.AcceptTcpClient();
Console.WriteLine("Connected!");
newThread = new Thread(new ThreadStart(newScream));
newThread.Start();
}
}
catch (SocketException e)
{
Console.WriteLine("SocketException: {0}", e);
}
finally
{
// Stop listening for new clients.
Console.WriteLine("Stop listening for new clients");
serverTcpListener.Stop();
}
Console.WriteLine("\nHit enter to continue...");
Console.Read();

}

static Int32 port = 9050;
static IPAddress localAddr = IPAddress.Parse("127.0.0.1");
static TcpListener serverTcpListener = null;
static Byte[] bytes = new Byte[256];
static String data = null;
static TcpClient client;
static void newScream()
{
data = null;
NetworkStream stream = client.GetStream();
stream.Write(Encoding.ASCII.GetBytes("Connected!"), 0, 10);
int i;
while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
{
data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
Console.WriteLine("Received: {0}", data);
data = data.ToUpper();
byte[] msg = System.Text.Encoding.ASCII.GetBytes(data);
stream.Write(msg, 0, msg.Length);
Console.WriteLine("Sent: {0}", data);
}
}
}
}
客户端：
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;

namespace mTcpClint
{
/// <summary>
/// Class1 的摘要说明。
/// </summary>
class client
{
/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main(string[] args)
{
//
// TODO: 在此处添加代码以启动应用程序
//
byte[] data = new byte[1024];
//Socket newclient = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
Console.Write("please input the server ip:");
string ipadd = Console.ReadLine();
Console.WriteLine();
Console.Write("please input the server port:");
int port = Convert.ToInt32(Console.ReadLine());
IPEndPoint ie = new IPEndPoint(IPAddress.Parse(ipadd), port);//服务器的IP和端口
TcpClient newclient;
newclient = new TcpClient();
newclient.Connect(ipadd, port);
int recv = newclient.Client.Receive(data);
string stringdata = Encoding.ASCII.GetString(data, 0, recv);
Console.WriteLine(stringdata);
while (true)
{
string input = Console.ReadLine();
if (input == "exit") break;
newclient.Client.Send(Encoding.ASCII.GetBytes(input));
data = new byte[1024];
recv = newclient.Client.Receive(data);
stringdata = Encoding.ASCII.GetString(data, 0, recv);
Console.WriteLine(stringdata);
}
Console.WriteLine("disconnect from server");
newclient.Client.Shutdown(SocketShutdown.Both);
newclient.Close();
}
}
}

Answer 2

1）根据MSDN文档，TcpClient的构造函数

public TcpClient(string hostname,int port)

参数：

hostname  类型：System.String  要连接到的远程主机的 DNS 名。

port 类型：System.Int32  要连接到的远程主机的端口号。

注意：第一个参数hostname，只能是域名或主机名；不能直接使用字符串 "172.18.9.114"

2）使用以下方法，可以绕开 Dns.GetHostName( )

using System.Net;
……
EndPoint ep = new new IPEndPoint(IPAddress.Parse("172.18.9.114"),  518888);
//使用TcpClient另一个构造函数 public TcpCleent(EndPoint ep)
client = new TcpClient(ep);
……

Answer 3

你看看返回的类型或者值是不是一样的，有可能值不一样啊。