Sun Java System Message Queue 4.3 Developer's Guide for C Clients

Defining Connection Properties

Connection properties specify the following information:

The following sections examine the effect of properties used to manage connection handling, reliability, message flow, and security.

Table 4–2 lists and describes all properties of a connection. For information on how to set and change connection properties, see Working With Properties.

Connection Handling

Connections to a message server are specified by a broker host name and port number.

The MQ_PING_INTERVAL_PROPERTY also affects connection handling. This property is set to the interval (in seconds) that the connection can be idle before the C client runtime pings the broker to test whether the connection is still alive. This property is useful for either producers who use the connection infrequently or for clients who are exclusive consumers, passively waiting for messages to arrive. The default value is 30 seconds. Setting an interval that is too low may result in some performance loss. The minimum permitted value is 1 second to prevent this from happening.

Currently, the C-API does not support auto-reconnect or failover, which allows the client runtime to automatically reconnect to a broker if a connection fails.


Two connection properties enable the acknowledgement of messages sent to the broker and of messages received from the broker. These are described in Message Acknowledgement. In addition to setting these properties, you can also set MQ_ACK_TIMEOUT_PROPERTY, which determines the maximum time that the client runtime will wait for any broker acknowledgement before throwing an exception.

Flow Control

A number of connection properties determine the use of Message Queue control messages by the client runtime. Messages sent and received by Message Queue clients and Message Queue control messages pass over the same client-broker connection. Because of this, delays may occur in the delivery of control messages, such as broker acknowledgements, if these are held up by the delivery of JMS messages. To prevent this type of congestion, Message Queue meters the flow of JMS messages across a connection.

You should keep the value of MQ_CONNECTION_FLOW_COUNT_PROPERTY low if the client is doing operations that require many responses from the broker; for example, the client is using the CLIENT_ACKNOWLEDGE or AUTO_ACKNOWLEDGE modes, persistent messages, transactions, or if the client is adding or removing consumers. You can increase the value of MQ_CONNECTION_FLOW_COUNT_PROPERTY without compromising performance if the client has only simple consumers on a connection using DUPS_OK mode.

The C API does not currently support consumer-based flow control.