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TCP Sockets
The low-level socket used to implement the higher-level HTTP protocol is exposed to
applications via the Generic Connection Framework. The usage is similar to the
examples above, however, a
Connection.open()
StreamConnection sc =
(StreamConnection)Connector.open(
"socket://www.motorola.com:8000");
Although similar to HTTP, notice the required port number at the end of the remote
address. In the previous protocols, those ports are well known and registered so they are
not required, but in the case of low level sockets, this value is not defined. The port
number is a required parameter for this protocol stack.
UDP Sockets
If networking efficiency is of greater importance than reliability, datagrams (UDP) sockets
are also available to the application in much the same manner as other networking
protocols. The
object, as is shown in the following example:
DatagramConnection dc = (DatagramConnection)Connector.open(
"datagram://170.169.168.167:8000");
Much like low-level sockets, accessing UDP requires both a target address and a port
number. The Motorola C370, C450, and C550 series of handsets supports a maximum
outgoing and incoming payload of 1472 bytes and 2944 bytes, respectively.
Implementation Notes
As stated in the previous sections, the Motorola C370, C450, and C550 series of
handsets supports some networking options. The networking options however are limited
by both memory and bandwidth, which place hard restrictions on the applications. These
limitations manifest themselves mainly in the number of simultaneous connections that
can be opened.
Maximum number of sockets is 5 of any combinations of HTTP and UDP. Due to memory
constraints, the C370, C450, and C550 can support only one secure session (i.e. if other
application like Browser already opened a secure socket, a KJava midlet will get an
IOException when it tries to open only one connection which is HTTP connection). If the
maximum number of sockets is concurrently opened by the application and a sixth socket
is requested, an exception is thrown to the calling application.
StreamConnection
method, as shown in the following example:
object in this case returns a
Connector
is returned by the
DatagramConnection
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