socks: fix incorrect port number in SOCKS4 error message

Prior to this change it appears the SOCKS5 port parsing was erroneously
used for the SOCKS4 error message, and as a result an incorrect port
would be shown in the error message.

Bug: https://github.com/curl/curl/issues/1892
Reported-by: Jackarain@users.noreply.github.com

lib/socks.c

@@ -306,7 +306,7 @@ CURLcode Curl_SOCKS4(const char *proxy_user,
             ", request rejected or failed.",
             (unsigned char)socksreq[4], (unsigned char)socksreq[5],
             (unsigned char)socksreq[6], (unsigned char)socksreq[7],
-            (((unsigned char)socksreq[8] << 8) | (unsigned char)socksreq[9]),
+            (((unsigned char)socksreq[2] << 8) | (unsigned char)socksreq[3]),
             (unsigned char)socksreq[1]);
       return CURLE_COULDNT_CONNECT;
     case 92:
@@ -316,7 +316,7 @@ CURLcode Curl_SOCKS4(const char *proxy_user,
             "identd on the client.",
             (unsigned char)socksreq[4], (unsigned char)socksreq[5],
             (unsigned char)socksreq[6], (unsigned char)socksreq[7],
-            (((unsigned char)socksreq[8] << 8) | (unsigned char)socksreq[9]),
+            (((unsigned char)socksreq[2] << 8) | (unsigned char)socksreq[3]),
             (unsigned char)socksreq[1]);
       return CURLE_COULDNT_CONNECT;
     case 93:
@@ -326,7 +326,7 @@ CURLcode Curl_SOCKS4(const char *proxy_user,
             "report different user-ids.",
             (unsigned char)socksreq[4], (unsigned char)socksreq[5],
             (unsigned char)socksreq[6], (unsigned char)socksreq[7],
-            (((unsigned char)socksreq[8] << 8) | (unsigned char)socksreq[9]),
+            (((unsigned char)socksreq[2] << 8) | (unsigned char)socksreq[3]),
             (unsigned char)socksreq[1]);
       return CURLE_COULDNT_CONNECT;
     default:
@@ -335,7 +335,7 @@ CURLcode Curl_SOCKS4(const char *proxy_user,
             ", Unknown.",
             (unsigned char)socksreq[4], (unsigned char)socksreq[5],
             (unsigned char)socksreq[6], (unsigned char)socksreq[7],
-            (((unsigned char)socksreq[8] << 8) | (unsigned char)socksreq[9]),
+            (((unsigned char)socksreq[2] << 8) | (unsigned char)socksreq[3]),
             (unsigned char)socksreq[1]);
       return CURLE_COULDNT_CONNECT;
     }