Add testcases

Signed-off-by: Thynson <lanxingcan@gmail.com>
add test-socket-02.c

Signed-off-by: Thynson <lanxingcan@gmail.com>
update test-socket-02.c as a echo server

Signed-off-by: Thynson <lanxingcan@gmail.com>
test link list

Signed-off-by: Thynson <lanxingcan@gmail.com>
test: auto close socket

Signed-off-by: Thynson <lanxingcan@gmail.com>