我正在嘗試運行在iOS 6教程：第1/2部分的Apple Push Notification Services中找到的Ray Wenderlich教程。我在本地目錄中創建了AppID和SSL證書以及密鑰和PEM文件。之后，我進入測試證書是否有效的步驟，并從此本地目錄調用了以下命令：$ openssl s_client -connect gateway.sandbox.push.apple.com:2195 -cert PushChatCert.pem -key PushChatKey.pem這產生了很多輸出。在輸出的中間是以下內容：verify error:num=20:unable to get local issuer certificateverify return:0這是錯誤，還是測試錯誤？如果是錯誤，將是什么原因或您將建議如何解決？這是完整的輸出（減去證書數據）：Enter pass phrase for PushChatKey.pem:    CONNECTED(00000003)depth=1 /C=US/O=Entrust, Inc./OU=www.entrust.net/rpa is incorporated by reference/OU=(c) 2009 Entrust, Inc./CN=Entrust Certification Authority - L1Cverify error:num=20:unable to get local issuer certificateverify return:0---Certificate chain 0 s:/C=US/ST=California/L=Cupertino/O=Apple Inc./OU=iTMS Engineering/CN=gateway.sandbox.push.apple.com   i:/C=US/O=Entrust, Inc./OU=www.entrust.net/rpa is incorporated by reference/OU=(c) 2009 Entrust, Inc./CN=Entrust Certification Authority - L1C 1 s:/C=US/O=Entrust, Inc./OU=www.entrust.net/rpa is incorporated by reference/OU=(c) 2009 Entrust, Inc./CN=Entrust Certification Authority - L1C   i:/O=Entrust.net/OU=www.entrust.net/CPS_2048 incorp. by ref. (limits liab.)/OU=(c) 1999 Entrust.net Limited/CN=Entrust.net Certification Authority (2048)---Server certificate-----BEGIN CERTIFICATE-----<Long string of data removed>-----END CERTIFICATE-----subject=/C=US/ST=California/L=Cupertino/O=Apple Inc./OU=iTMS Engineering/CN=gateway.sandbox.push.apple.comissuer=/C=US/O=Entrust, Inc./OU=www.entrust.net/rpa is incorporated by reference/OU=(c) 2009 Entrust, Inc./CN=Entrust Certification Authority - L1C---No client certificate CA names sent---SSL handshake has read 2731 bytes and written 2215 bytes---New, TLSv1/SSLv3, Cipher is AES256-SHAServer public key is 2048 bitSecure Renegotiation IS supportedCompression: NONEExpansion: NONE該教程繼續說：“如果連接成功，您應該可以輸入幾個字符。按Enter鍵時，服務器應該斷開連接。” 我能夠做到這一點，并且服務器已斷開連接。但是本教程繼續說，您可能必須查看輸出以發現錯誤。因此，這個問題的原因。