Visual Basic.NET How to Program (PDF)

1106 Networking: Streams-Based Sockets and Datagrams Chapter 22
71 ' handle exception if error occurs in sending data to server
72 Catch exception As SocketException
73 txtDisplay.Text &= vbCrLf & "Error writing object"
74 End Try
75
76 End Sub ' txtInput_KeyDown
77
78 ' connect to server and display server-generated text
79 Public Sub RunClient()
80 Dim client As TcpClient
81
82 ' instantiate TcpClient for sending data to server
83 Try
84
85 txtDisplay.Text &= "Attempting connection" & vbCrLf
86
87 ' Step 1: create TcpClient and connect to server
88 client = New TcpClient()
89 client.Connect("localhost", 5000)
90
91 ' Step 2: get NetworkStream associated with TcpClient
92 output = client.GetStream()
93
94 ' create objects for writing and reading across stream
95 writer = New BinaryWriter(output)
96 reader = New BinaryReader(output)
97
98 txtDisplay.Text &= vbCrLf & "Got I/O streams" & vbCrLf
99
100 txtInput.ReadOnly = False
101
102 ' Step 3: processing phase
103 Try
104
105 ' loop until server signals termination
106 Do
107
108 ' read message from server
109 message = reader.ReadString
110 txtDisplay.Text &= vbCrLf & message
111
112 Loop While message "SERVER>>> TERMINATE"
113
114 ' handle exception if error in reading server data
115 Catch inputOutputException As IOException
116 MessageBox.Show("Client application closing")
117
118 ' Step 4: close connection
119 Finally
120
121 txtDisplay.Text &= vbCrLf & "Closing connection." & _
122 vbCrLf
123
Fig. 22.2 Client portion of a client/server stream-socket connection (part 3 of 5).