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TcpClient Constructor (String, Int32)

Initializes a new instance of the TcpClient class and connects to the specified port on the specified host.

Namespace:  System.Net.Sockets
Assembly:  System (in System.dll)

public TcpClient(
	string hostname,
	int port


Type: System.String

The DNS name of the remote host to which you intend to connect.

Type: System.Int32

The port number of the remote host to which you intend to connect.


The hostname parameter is null.


The port parameter is not between MinPort and MaxPort.


An error occurred when accessing the socket. See the Remarks section for more information.

This constructor creates a new TcpClient and makes a synchronous connection attempt to the provided host name and port number. The underlying service provider will assign the most appropriate local IP address and port number. TcpClient will block until it either connects or fails. This constructor allows you to initialize, resolve the DNS host name, and connect in one convenient step.

If IPv6 is enabled and the TcpClient(String, Int32) method is called to connect to a host that resolves to both IPv6 and IPv4 addresses, the connection to the IPv6 address will be attempted first before the IPv4 address. This may have the effect of delaying the time to establish the connection if the host is not listening on the IPv6 address.


If you receive a SocketException, use SocketException.ErrorCode to obtain the specific error code. After you have obtained this code, you can refer to the Windows Sockets version 2 API error code documentation in MSDN for a detailed description of the error.


This member outputs trace information when you enable network tracing in your application. For more information, see Network Tracing.

The following code example demonstrates how to create an instance of the TcpClient class using a host name and port number.

//Creates a TCPClient using host name and port.
TcpClient tcpClientB = new TcpClient ("", 11000);
// Creates a TCPClient using hostname and port.
TcpClient* tcpClientB = new TcpClient(S"", 11000);

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0