Why should start two virtual machines to run the program properly

When I choose to run their own program, start a virtual machine.
Then when the virtual machine is powered on, and then prompts the program fails to load, and then he started a new virtual machine.
This time, I was able to normal operating procedures.
In other words, every time I debugger, all must first start two virtual machines. Run the program on a new virtual machine.
Sometimes, the first virtual machine, and will not work.

I was very surprised.
Please help analyze, this is what happens.<-! Main posts under Banner (D4) -><-! Posts under the main text (D5) ->
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Version of the problem may be the simulator. Your version of the application is higher than the default simulator.
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I am also the case, I do not know how to solve.
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Before and after the start of even a simulator is the same version of it?
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reference to the third floor tantahe reply:

started before even a simulator is the same version of it?

Is the same version, because I have only one version of the simulator.
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Kazakhstan is a bit strange.
Try first simulator run up, and then run application.
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references, 5th Floor tantahe reply:

is strange Kazakhstan.
Try first simulator run up, and then run application.

Tried, not ah.
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First full start the emulator, running projects
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I already know why, because the occupation of the port.
I was watching the video, again learning.
Thunderbolt port and simulator port conflict, resulting in the first simulator conflict.