See libxtrans commit 0794b1b712a90b40e2b019c9edc6f96874493c52. The code to generate this socket was removed 5 years ago and even before it was conditional on #define TEST_t. There is no reference to that #define in either the X server nor libX11's git history, or in any of the current libX*. Let's assume this is well and truly obsolete.
System and Service Manager
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