用cocoapod导入库失败 需要spec

[731704267]

[!] Unable to satisfy the following requirements:

• CocoaAsyncSocket (~> 7.4.3) required by Podfile
• CocoaAsyncSocket (~> 7.4.3) required by Podfile
• CocoaAsyncSocket (~> 7.4.3) required by Podfile
• CocoaAsyncSocket (~> 7.4.3) required by Podfile

None of your spec sources contain a spec satisfying the dependency: CocoaAsyncSocket (~> 7.4.3).

You have either:

• out-of-date source repos which you can update with pod repo update.
• mistyped the name or version.
• not added the source repo that hosts the Podspec to your Podfile.

Note: as of CocoaPods 1.0, pod repo update does not happen on pod install by default.

用cocoapod导入第三方库的时候提示的，应该怎么获得spec？