TCP Transport Reference

Using ActiveMQ Classic > Configuring Transports > ActiveMQ Classic Connection URIs > TCP Transport Reference

The TCP Transport

The TCP transport allows clients to connect to a remote ActiveMQ Classic broker using a TCP socket. These configuration options can be used to tune the underlying TCP transport on either the client-side using the JMS client’s connection URI string or on a broker’s transport connector URI.

Note: Use Correct Prefix!

The options below should be prefixed with transport.* when used on a broker’s transport connector definition. On the client-side, however, the transport.* prefix must be omitted.

Configuration Syntax



Broker side (in TransportConnector):


Client side (in brokerURL):


Transport Options
Option Name Default Value Description
backlog 5000 Specifies the maximum number of connections waiting to be accepted by the transport server socket.
closeAsync true If true the socket close call happens asynchronously. This parameter should be set to false for protocols like STOMP, that are commonly used in situations where a new connection is created for each read or write. Doing so ensures the socket close call happens synchronously. A synchronous close prevents the broker from running out of available sockets owing to the rapid cycling of connections. 
connectionTimeout 30000 If >=1 the value sets the connection timeout in milliseconds. A value of 0 denotes no timeout. Negative values are ignored.
daemon false If true the transport thread will run in daemon mode. Set this parameter to true when embedding the broker in a Spring container or a web container to allow the container to shut down correctly.
dynamicManagement false If true the TransportLogger can be managed by JMX.
ioBufferSize 8 * 1024 Specifies the size of the buffer to be used between the TCP layer and the OpenWire layer where wireFormat based marshaling occurs.
jmxPort 1099 (Client Only) Specifies the port that will be used by the JMX server to manage the TransportLoggers. This should only be set, via URI, by either a client producer or consumer as the broker creates its own JMX server. Specifying an alternate JMX port is useful for developers that test a broker and client on the same machine and need to control both via JMX.
keepAlive false If true, enables TCP KeepAlive on the broker connection to prevent connections from timing out at the TCP level. This should not be confused with KeepAliveInfo messages as used by the InactivityMonitor.
logWriterName default Sets the name of the org.apache.activemq.transport.LogWriter implementation to use. Names are mapped to classes in the resources/META-INF/services/org/apache/activemq/transport/logwriters directory.
maximumConnections Integer.MAX_VALUE The maximum number of sockets allowed for this broker.
minmumWireFormatVersion 0 The minimum remote wireFormat version that will be accepted (note the misspelling). Note: when the remote wireFormat version is lower than the configured minimum acceptable version an exception will be thrown and the connection attempt will be refused. A value of 0 denotes no checking of the remote wireFormat version.
socketBufferSize 64 * 1024 Sets the size, in bytes, for the accepted socket’s read and write buffers.
soLinger Integer.MIN_VALUE Sets the socket’s option soLinger when the value is > -1. When set to -1 the soLinger socket option is disabled.
soTimeout 0 Sets the socket’s read timeout in milliseconds. A value of 0 denotes no timeout.
soWriteTimeout 0 Sets the socket’s write timeout in milliseconds. If the socket write operation does not complete before the specified timeout, the socket will be closed. A value of 0 denotes no timeout.
stackSize 0 Set the stack size of the transport’s background reading thread. Must be specified in multiples of 128K. A value of 0 indicates that this parameter is ignored.
startLogging true If true the TransportLogger object of the Transport stack will initially write messages to the log. This parameter is ignored unless trace=true.
tcpNoDelay false If true the socket’s option TCP_NODELAY is set. This disables Nagle’s algorithm for small packet transmission.
threadName N/A When this parameter is specified the name of the thread is modified during the invocation of a transport. The remote address is appended so that a call stuck in a transport method will have the destination information in the thread name. This is extremely useful when using thread dumps for degugging.
trace false Causes all commands that are sent over the transport to be logged. To view the logged output define the Log4j logger:
trafficClass 0 The Traffic Class to be set on the socket.
diffServ 0 (Client only) The preferred Differentiated Services traffic class to be set on outgoing packets, as described in RFC 2475. Valid integer values: [0,64]. Valid string values: EF, AF[1-3][1-4] or CS[0-7]. With JDK 6, only works when the JVM uses the IPv4 stack. To use the IPv4 stack set the system property Note: it’s invalid to specify both ‘diffServ and typeOfService’ at the same time as they share the same position in the TCP/IP packet headers
typeOfService 0 (Client only) The preferred Type of Service value to be set on outgoing packets. Valid integer values: [0,256]. With JDK 6, only works when the JVM is configured to use the IPv4 stack. To use the IPv4 stack set the system property Note: it’s invalid to specify both ‘diffServ and typeOfService’ at the same time as they share the same position in the TCP/IP packet headers.
useInactivityMonitor true When false the InactivityMonitor is disabled and connections will never time out.
useKeepAlive true When true KeepAliveInfo messages are sent on an idle connection to prevent it from timing out. If this parameter is false connections will still timeout if no data was received on the connection for the specified amount of time.
useLocalHost false When true local connections will be made using the value localhost instead of the actual local host name. On some operating systems, such as OS X, it’s not possible to connect as the local host name so localhost is better.
useQueueForAccept true When true accepted sockets are placed onto a queue for asynchronous processing using a separate thread.
wireFormat default The name of the wireFormat factory to use.
wireFormat.* N/A Properties with this prefix are used to configure the wireFormat.

See Configuring Wire Formats for more information.

Differentiated Services or Types of Service

There is support for setting Differentiated Services - as outlined in IETF RCF 2475. In order to configure the broker so that all outgoing packets from the broker match the DSCP values set on incoming packets - you will need to apply IP Tables scripts - found here.

Apache, ActiveMQ, Apache ActiveMQ, the Apache feather logo, and the Apache ActiveMQ project logo are trademarks of The Apache Software Foundation. Copyright © 2024, The Apache Software Foundation. Licensed under Apache License 2.0.