Resolve hostname as IP

[garaemon]

prosilica::Camera only read ip address. Need to resolve hostname as IP to pass it to prosilica::Camera

[wjwwood]

Why do you have to cast it to an struct in_addr rather than leave it as the normal char ** that it normally returns? I'm referencing this document:

http://www.gnu.org/software/libc/manual/html_node/Host-Names.html

Also, if you must cast it, please use the c++ style static_cast.

[wjwwood]

The patch seems reasonable to me, other than my minor comments.

[garaemon]

Updated

about in_addr issue, as described in here h_addr and h_addr_list are char* and char** but it's really in_addr*.

[wjwwood]

I see, makes sense. I'll let @trainman419 merge.

[trainman419]

This should probably include some kind of error handling and a useful message if the hostname lookup fails. As currently implemented, if the hostname lookup fails, it just passes the hostname to the prosilica library.

Re-using the ~ip_address parameter to specify a hostname is not a straightforward API, but I'm also hesitant to introduce another parameter. @wjwwood or @garaemon do you have any suggestions on better parameter usage?

[garaemon]

I wrote a simple testcode of gethostbyname and result is:

$ ./a.out                   
[OK]    localhost => 127.0.0.1
[OK]    127.0.0.1 => 127.0.0.1
[OK]    google.com(DNS lookup) => 173.194.117.231
[OK]    hrp2007v(writtein in /etc/hosts) => 10.7.3.12
[OK]    192.168.96.100 => 192.168.96.100
[ERROR] Failed to resolve 192.168.96.100a (malformed IP)
[ERROR] Failed to resolve 192.168.96.1000 (malformed IP)

Legal IP should be successfully resolved as the same IP.
I think re-using ~ip_address does not effect existing code which is working now.

And it can detect hostname (and malformed IP address) by return value of gethostbyname.
Should it output some error messages?

[trainman419]

I know how gethostbyname works. I know that it will accept an IP address and produce the correct result.

I'm worried that users won't realize that they can supply a hostname in the ip_address parameter, because the parameter name implies that the node is only expecting an IP address. This is why I think there should be a new, explicit hostname parameter, so that future users know that they're allowed to specify their camera by hostname.

You should include explicit error-handling for when the gethostbyname call fails, with a concise and readable message indicating that it tired to do a hostname lookup, and that the hostname lookup failed.

[garaemon]

I see.

Let me summarize;

• Keep ~ip_address as a parameter to specify IP address directly
• Add new ~hostname parameter to resolve hostname and IP address with error handling

[garaemon]

Updated

• Keep ~ip_address without hostname resolving

• Add ~hostname parameter to resolve hostname by gethostbyname

• If failed to resolve hosname, print error

• Specifying ~ip_address:=chestcamera, it should not be resolved

  [INFO] [1435917691.82] [/chest_camera] Trying to load camera with ipaddress: chestcamera
  [WARN] [1435917695.82] [/chest_camera] Unable to open prosilica camera with ip address chestcamera: Unable to find requested camera: 
                                     Timeout during wait
  [INFO] [1435917695.82] [/chest_camera] Available cameras:
  02-2171A-07131 - GC2450C - Unique ID = 115847 IP = 192.168.96.116
  

• Specifying ~hostname:=chestcamera, it should be resolved

  [INFO] [1435917858.62] [/chest_camera] Trying to load camera with hostname: chestcamera
  [INFO] [1435917858.62] [/chest_camera] hostname resolved as 192.168.96.116
  [INFO] [1435917858.94] [/chest_camera] Started Prosilica camera with guid "115847"
  [INFO] [1435917861.94] [/chest_camera] Loaded calibration for camera 'prosilica115847'
  [INFO] [1435917861.94] [/chest_camera] starting camera 115847 in freerun trigger mode
  [INFO] [1435917862.30] [/chest_camera] starting camera 115847 in fixedrate trigger mode
  

• Specifying ~hostname:=chestcameraa, it should be resolved but be failed

  [INFO] [1435917966.09] [/chest_camera]  Trying to load camera with hostname: chestcameraaa
  [FATAL] [1435917966.12] [/chest_camera] Failed to resolve hostname: chestcameraaa
  [WARN] [1435917966.12] [/chest_camera]  Unable to open prosilica camera with hostname chestcameraaa: Failed to resolve hostname
  [INFO] [1435917966.12] [/chest_camera]  Available cameras:
  02-2171A-07131 - GC2450C - Unique ID = 115847 IP = 192.168.96.116