pcl_ros::transformPointCloud says it does not have the transformation

edit

Hi all, I am using the pcl_ros package in Groovy in order to transform a point cloud in the /map frame (/map -> /odom is given by a localizer node, while /odom -> /rgb_optical_frame is given by a set of transform publishers):

pcl_ros::transformPointCloud(fixedFrame, *cloud, *tcloud, tf_);

However, an exception is raised that says I do not have the transormation from /rgb_optical_frame to /map. If I open rqt and display the transformation tree, this is all connected as expected.

Could it be some issues about timings? How to check them, how to solve?

EDIT: here I add some additional information from the comments I have two machines, on the first machine (I call it sensor-laptop) the following topics are computed: - tf (/map -> /odom, /odom -> /X1_rgb_optical_frame) - point clouds from depth and rgb images

on the second machine (visualization-laptop) I compute the following topics: - point clouds (again) from depth and rgb images sent over the network from sensor-laptop and I am trying to visualize these point clouds using the transformation computed on the other laptop

the two laptops are time-synchronized using chrony, however, the transformPointCloud function says it does not have the transformation:

[ERROR] [1408639544.612446512]: Unable to lookup transform, cache is empty, when looking up transform from frame [/X1_rgb_optical_frame] to frame [/map]

EDIT2: the output of tf_echo and tf_monitor on the visualizer-laptop these outputs have been obtained on visualizer-laptop by setting ROS_MASTER_URI to the address of sensor-laptop

$ rosrun tf tf_echo /map /X1_rgb_optical_frame
Failure at 1408704324.631461344
Exception thrown:Could not find a connection between '/map' and '/X1_rgb_optical_frame' because they are not part of the same tree.Tf has two or more unconnected trees.
The current list of frames is:
Frame /X1_depth_optical_frame exists with parent /X1_depth_frame.
Frame /X1_depth_frame exists with parent /X1_link.
Frame /X2_depth_frame exists with parent /X2_link.
Frame /X2_link exists with parent /base_link.
Frame /X2_depth_optical_frame exists with parent /X2_depth_frame.
Frame /X1_link exists with parent /base_link.
Frame /base_link exists with parent /base_projected.
Frame /X1_rgb_frame exists with parent /X1_link.
Frame /X2_rgb_frame exists with parent /X2_link.
Frame /X2_rgb_optical_frame exists with parent /X2_rgb_frame.
Frame /base_projected exists with parent NO_PARENT.
Frame /imu exists with parent /base_link.
Frame /X1_rgb_optical_frame exists with parent /X1_rgb_frame.
Frame /odom exists with parent /map.
Frame /map exists with parent NO_PARENT.

At time 1408704324.660
- Translation: [0.110, 0.045, 0.540]
- Rotation: in Quaternion [0.496, 0.504, 0.503, 0.497]
            in RPY [1.571, 0.002, 1.585]
At time 1408704324.660
- Translation: [0.110, 0.045, 0.540]
- Rotation: in Quaternion [0.496, 0.504, 0.503, 0.497]
            in RPY [1.571, 0.002, 1.585]
At time 1408704326.660
- Translation: [0.110, 0.045, 0.540]
- Rotation: in Quaternion [0.496, 0.504, 0.503, 0.497]
            in RPY [1.571, 0.002, 1.585]
At time 1408704326.660
- Translation: [0.110, 0.045, 0.540]
- Rotation: in Quaternion [0.496, 0.504, 0.503, 0.497]
            in RPY [1.571, 0.002, 1.585]
At time 1408704328.663
- Translation: [0.110, 0.045, 0.540]
- Rotation: in ...