TcpClient.Connect(String, Int32)和TcpClient.Connect(IPAddress, Int32)的区别

Question

TcpClient tc = new TcpClient();
            IPAddress test = IPAddress.Parse("192.168.1.100");
            tc.Connect(test, 80);和
tc.Connect("192.168.1.100", 80);

Answer 1

两者的源码：public void Connect(string hostname, int port)
{
    if (Logging.On)
    {
        Logging.Enter(Logging.Sockets, this, "Connect", hostname);
    }
    if (this.m_CleanedUp)
    {
        throw new ObjectDisposedException(base.GetType().FullName);
    }
    if (hostname == null)
    {
        throw new ArgumentNullException("hostname");
    }
    if (!ValidationHelper.ValidateTcpPort(port))
    {
        throw new ArgumentOutOfRangeException("port");
    }
    if (this.m_Active)
    {
        throw new SocketException(SocketError.IsConnected);
    }
    IPAddress[] hostAddresses = Dns.GetHostAddresses(hostname);
    Exception exception = null;
    Socket socket = null;
    Socket socket2 = null;
    try
    {
        if (this.m_ClientSocket == null)
        {
            if (Socket.OSSupportsIPv4)
            {
                socket2 = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            }
            if (Socket.OSSupportsIPv6)
            {
                socket = new Socket(AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp);
            }
        }
        foreach (IPAddress address in hostAddresses)
        {
            try
            {
                if (this.m_ClientSocket == null)
                {
                    if ((address.AddressFamily == AddressFamily.InterNetwork) && (socket2 != null))
                    {
                        socket2.Connect(address, port);
                        this.m_ClientSocket = socket2;
                        if (socket != null)
                        {
                            socket.Close();
                        }
                    }
                    else if (socket != null)
                    {
                        socket.Connect(address, port);
                        this.m_ClientSocket = socket;
                        if (socket2 != null)
                        {
                            socket2.Close();
                        }
                    }
                    this.m_Family = address.AddressFamily;
                    this.m_Active = true;
                    goto Label_01BF;
                }
                if (address.AddressFamily == this.m_Family)
                {
                    this.Connect(new IPEndPoint(address, port));
                    this.m_Active = true;
                    goto Label_01BF;
                }
            }
            catch (Exception exception2)
            {
                if (((exception2 is ThreadAbortException) || (exception2 is StackOverflowException)) || (exception2 is OutOfMemoryException))
                {
                    throw;
                }
                exception = exception2;
            }
        }
    }
    catch (Exception exception3)
    {
        if (((exception3 is ThreadAbortException) || (exception3 is StackOverflowException)) || (exception3 is OutOfMemoryException))
        {
            throw;
        }
        exception = exception3;
    }
    finally
    {
        if (!this.m_Active)
        {
            if (socket != null)
            {
                socket.Close();
            }
            if (socket2 != null)
            {
                socket2.Close();
            }
            if (exception != null)
            {
                throw exception;
            }
            throw new SocketException(SocketError.NotConnected);
        }
    }
Label_01BF:
    if (Logging.On)
    {
        Logging.Exit(Logging.Sockets, this, "Connect", (string) null);
    }
}public void Connect(IPAddress address, int port)
{
    if (Logging.On)
    {
        Logging.Enter(Logging.Sockets, this, "Connect", address);
    }
    if (this.m_CleanedUp)
    {
        throw new ObjectDisposedException(base.GetType().FullName);
    }
    if (address == null)
    {
        throw new ArgumentNullException("address");
    }
    if (!ValidationHelper.ValidateTcpPort(port))
    {
        throw new ArgumentOutOfRangeException("port");
    }
    IPEndPoint remoteEP = new IPEndPoint(address, port);
    this.Connect(remoteEP);
    if (Logging.On)
    {
        Logging.Exit(Logging.Sockets, this, "Connect", (string) null);
    }
}

Answer 2

简化一下，其源代码基本上是这样的IPAddress[] hostAddresses = Dns.GetHostAddresses(hostname);
Socket socket = null;
Socket socket2 = null;
if (this.m_ClientSocket == null)
{
    if (Socket.OSSupportsIPv4)
    {
        socket2 = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
    }
    if (Socket.OSSupportsIPv6)
    {
        socket = new Socket(AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp);
    }
}
foreach (IPAddress address in hostAddresses)
{
    if ((address.AddressFamily == AddressFamily.InterNetwork) && (socket2 != null)) //使用ipv4
    {
        socket2.Connect(address, port);
        this.m_ClientSocket = socket2;
        if (socket != null)
        {
            socket.Close();
        }
    }
    else if (socket != null)    //使用ipv6
    {
        socket.Connect(address, port);
        this.m_ClientSocket = socket;
        if (socket2 != null)
        {
            socket2.Close();
        }
    }
}

Answer 3

IPAddress test = IPAddress.Parse("192.168.1.100");
tc.Connect(test, 80);
这个里面只可以是IP地址字符串。不能写成IPAddress.Parse("www.baidu.com");
tc.Connect("192.168.1.100", 80);这个里面可以是IP字符串，也可以是主机，比如www.baidu.com

Answer 4

源代码都给你了还不会看……
Connect(String, Int32)会将这个主机或IP的字符串转化为IPAddress的一个数组，然后遍历这个循环，根据不同情况，可能调用Connect(IPAddress, Int32)，也可能调用Connect(IPEndPoint)
而Connect(IPAddress, Int32)调用的是Connect(IPEndPoint)
所以，就你的提问，这两个方法最终都会调用Connect(IPEndPoint)，只是传入字符串的话会做更多的操作……明白了不……

Answer 5

那如果tc.Connect("192.168.1.100", 80);不通
TcpClient tc = new TcpClient();
            IPAddress test = IPAddress.Parse("192.168.1.100");
            tc.Connect(test, 80);
肯定不通吧？
现在是tc.Connect("192.168.1.100", 80);不通 但是TcpClient tc = new TcpClient();
            IPAddress test = IPAddress.Parse("192.168.1.100");
            tc.Connect(test, 80);
能通

Answer 6

那可真不一定，Connect(string hostname, int port)
看函数签名，这个string参数应该传入的是主机名，而不是IP

Answer 7

可见你没有看懂代码  IPAddress[] hostAddresses = Dns.GetHostAddresses(hostname);

Answer 8

人家可以仿照源代码，来通过dns类来获得IPAddress啊。学.ney还是要以自己独立看懂一些源代码为基础能力，而不是听一般的所谓解释。