Added a note regarding select on Linux.

Core/HLE/proAdhoc.cpp

@@ -298,8 +298,11 @@ int IsSocketReady(int fd, bool readfd, bool writefd, int* errorcode, int timeout
 	timeval tval;
 
 	// Avoid getting Fatal signal 6 (SIGABRT) on linux/android
-	if (fd < 0)
-	    return SOCKET_ERROR;
+	if (fd < 0) {
+		if (errorcode != nullptr)
+			*errorcode = EBADF;
+		return SOCKET_ERROR;
+	}
 
 	FD_ZERO(&readfds);
 	writefds = readfds;
@@ -312,9 +315,10 @@ int IsSocketReady(int fd, bool readfd, bool writefd, int* errorcode, int timeout
 	tval.tv_sec = timeoutUS / 1000000;
 	tval.tv_usec = timeoutUS % 1000000;
 
+	// Note: select will flags an unconnected TCP socket (ie. a freshly created socket without connecting first, or when connect failed with ECONNREFUSED on linux) as writeable/readable, thus can't be used to tell whether the connection has established or not.
 	int ret = select(fd + 1, readfd? &readfds: nullptr, writefd? &writefds: nullptr, nullptr, &tval);
 	if (errorcode != nullptr)
-		*errorcode = errno;
+		*errorcode = (ret < 0? errno: 0);
 
 	return ret;
 }

Core/HLE/proAdhoc.h

@@ -63,6 +63,7 @@
 #undef ECONNREFUSED
 #undef ENETUNREACH
 #undef ENOTCONN
+#undef EBADF
 #undef EAGAIN
 #undef EINPROGRESS
 #undef EISCONN
@@ -76,6 +77,7 @@
 #define ECONNREFUSED WSAECONNREFUSED
 #define ENETUNREACH WSAENETUNREACH
 #define ENOTCONN WSAENOTCONN
+#define EBADF WSAEBADF
 #define EAGAIN WSAEWOULDBLOCK
 #define EINPROGRESS WSAEWOULDBLOCK
 #define EISCONN WSAEISCONN

Core/HLE/sceNetAdhoc.cpp

@@ -831,6 +831,21 @@ int DoBlockingPtpConnect(AdhocSocketRequest& req, s64& result, AdhocSendTargets&
 			if (RecreatePtpSocket(req.id) < 0) {
 				WARN_LOG(SCENET, "sceNetAdhocPtpConnect[%i:%u]: Failed to Recreate Socket", req.id, ptpsocket.lport);
 			}
+
+			u64 now = (u64)(time_now_d() * 1000000.0);
+			if (req.timeout == 0 || now - req.startTime <= req.timeout) {
+				// Try again later
+				return -1;
+			}
+			else {
+				// Handle Workaround that force the first Connect to be blocking for issue related to lobby or high latency networks
+				if (sock->nonblocking)
+					result = ERROR_NET_ADHOC_WOULD_BLOCK;
+				else
+					result = ERROR_NET_ADHOC_TIMEOUT; // FIXME: PSP never returned ERROR_NET_ADHOC_TIMEOUT on PtpConnect? or only returned ERROR_NET_ADHOC_TIMEOUT when the host is too busy? Seems to be returning ERROR_NET_ADHOC_CONNECTION_REFUSED on timedout instead (if the other side in not listening yet, which is similar to BSD).
+				
+				return 0;
+			}
 		}
 	}
 	// Check if the connection has completed (assuming "connect" has been called before)