After establishing a connection you may write data to the server by getting the java.io.OutputStream associated with the connection. To get the output stream invoke the IpClient#getOutputStream method.
Example
// create new IpClient instance
IpClient client = new IpClient("www.yahoo.com",80);
// establish connection
client.connect();
// get output stream
OutputStream out = client.getOutputStream();
// send data
String command = "GET / HTTP/1.0\r\n\r\n";
out.write(command.getBytes());
out.flush();
// get input stream
InputStream in = client.getInputStream();
// read data from server
int i = 0;
while((i = in.read()) != -1) {
System.out.print((char)i);
}