[client] Input values should be validated strictly

[ashie]

Currently most input values aren't validated properly. For example, range of a value for server port should be 1 to 65535.

[cosmo0920]

Here is a few strategy candidates:

• More using parametrized tests. cutter has this feature.
• Use QuickCheck inspired test library.
  • theoretically, QuickCheck is enough to test in most cases. original paper: http://www.cs.tufts.edu/~nr/cs257/archive/john-hughes/quick.
• More strict test case generation, it seems to be useful z3. Z3 is a theorem prover from Microsoft Research.