Listener configuration

The TCP transport listener is configured in axis2.xml using the following declaration:

<transportReceiver name="tcp" class="org.apache.axis2.transport.tcp.TCPTransportListener"/>

Depending on how the TCP transport is set up, additional parameters may be required inside the transportReceiver element (see next section).

Endpoint configuration

Endpoints can be configured both at the transport level and at the service level. Each endpoint opens a TCP server socket for listening. TCP requests received on a port that is configured on a service will be pre-dispatched to that service. Packets received by a port that is configured at the transport level need to be dispatched using one of the following mechanisms:

1. Using the namespace URI of the first child element of SOAPBody (SOAPMessageBodyBasedDispatcher).
2. Using WS-Addressing headers (SOAPActionBasedDispatcher).

   Endpoints are configured by adding parameter elements to the transportReceiver element in axis2.xml or to a service element in an services.xml file. The set of parameters is the same for both scenarios:

   transport.tcp.port (required)

   The port number over which the TCP server socket should be opened.

   transport.tcp.hostname (optional)

   The hostname to which the TCP server socket should be bound.

   transport.tcp.contentType (optional, defaults to text/xml)

   Specifies the content type of the messages received on the endpoint.

   transport.tcp.backlog (optional, defaults to 50)

   The length of the backlog (queue) supported by the TCP server socket.

Enabling TCP listener at the transport level

The following declaration in axis2.xml initializes a TCP server socket on port 6060 and allows all services (for which TCP is in the list of exposed transports) to receive messages over that port:

<transportReceiver name="tcp" class="org.apache.axis2.transport.tcp.TCPTransportListener">
  <parameter name="transport.tcp.port">6060</parameter>
</transportReceiver>

For this to work, WS-Addressing must be enabled, and messages sent to port 6060 must have the relevant WS-Addressing headers.

<module ref="addressing"/>

With the configuration shown above, the TCP transport would generate bindings with the following EPR:

tcp://localhost:6060/services/Version?contentType=text/xml

Similar EPRs will be generated for services when the transport is configured at service level.

The following example shows a message that can be sent to the Version service over TCP:

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
                   xmlns:wsa="http://www.w3.org/2005/08/addressing">
    <SOAP-ENV:Header>
        <wsa:MessageID>1234</wsa:MessageID>
        <wsa:To>tcp://localhost:6060/services/Version?contentType=text/xml</wsa:To>
        <wsa:Action>urn:getVersion</wsa:Action>
    </SOAP-ENV:Header>
    <SOAP-ENV:Body>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Axis2 client API can be used to easily send TCP requests to a remote service. The following code snippet shows how to do that. The TCP transport sender must be enabled in the axis2.xml in order for this to work.

String url = "tcp://localhost:6060/services/Version?contentType=text/xml";
OMElement payload = ...

ServiceClient serviceClient = new ServiceClient();
Options options = new Options();
EndpointReference targetEPR = new EndpointReference(url);
options.setTo(targetEPR);
serviceClient.setOptions(options);
OMElement response = serviceClient.sendReceive(payload);

The transport sender that should be invoked is inferred from the targetEPR (tcp://...). In this case it is TCP and the listener is also TCP. The SOAP message has to be self contained in order to use Addressing. The parameter is of the type OMElement, the XML representation of Axis2.

A TCP URL may contain an optional timeout value, as a query parameter, to indicate how long (in milliseconds) the client should wait for a response. Once this period has expired, the client TCP socket will timeout:

tcp://localhost:6060/services/Version?contentType=text/xml&timeout=10000

If the Axis2 client API is used to send a request to the above URL, the client socket will timeout after waiting for 10 seconds, for the response.