TCPROS

TCPROS is a transport layer for ROS Messages and Services. It uses standard TCP/IP sockets for transporting message data. Inbound connections are received via a TCP Server Socket with a header containing message data type and routing information. For more information about this header format, see Connection Header.

TODO: more information about wire protocol

TCPROS Header Fields

Inbound connections to a TCPROS Server Socket are routed by information contained within the header fields. If the header contains the 'topic' field, it will be routed as a connection to a ROS Publisher. If it contains a 'service' field, it will be routed as a connection to a ROS Service.

A TCPROS subscriber is required to send the following fields:

• callerid: name of subscriber
• topic: name of the topic the subscriber is connecting to
• md5sum: md5sum of the message type
• type: message type

A TCPROS publisher is required to reply with the following fields on a successful connection:

• md5sum: md5sum of the message type
• type: message type

A TCPROS service client is required to send the following fields:

• callerid: node name of service client
• service: name of the topic the subscriber is connecting to
• md5sum: md5sum of the message type
• type: service type

A TCPROS subscriber may optionally send the following fields:

• tcp_nodelay: if '1', indicates that the publisher should set TCP_NODELAY on the socket, if possible.

A TCPROS publisher may optionally send the following fields:

• callerid: name of publisher. Although this field is not required, it is highly recommended for debugging purposes.
• latching: if '1', indicates that the publisher is sending latched messages. The protocol for exchanging latched messages is identical, but subscribers may wish to take note of the latched status.

A TCPROS service client may optionally send the following fields:

• persistent: if '1', indicates that the service connection should be kept open for multiple service requests

A TCPROS Service is required to reply with the following fields on a successful connection:

• callerid: node name of Service

TCPROS has the following optional fields:

• message_definition: full text of message definition (output of gendeps --cat)
• error: human-readable error message if the connection is not successful

Service-specific

Services include an 'ok' byte in response to each service request message.

If the ok byte is true (1), it must be followed by a serialized string (same length + bytes format that ROS messages use for serializing strings).

If the ok byte is false (0), it must be followed by the service response message.