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  • is it valid that a state machine can have more than one possible state for some transition?

    - by shankbond
    I have a requirement for a workflow which I am trying to model as a state machine, I see that there is more than one outcome of a given transition(or activity). Is it valid for a state machine to have more than one possible states, but only one state will be true at a given time? Note: This is my first attempt to model a state machine. Eg. might be: s1-t1-s2 s1-t1-s3 s1-t1-s4 where s1, s2, s3, s4 are states and t1 is transition/activity. A fictitious real world example might be: For a human, there can be two states: hungry, not hungry A basket can have only one item from: apple, orange. So, to model it we will have: hungry-pick from basket-apple found hungry-pick from basket-orange found apple found-eat-not hungry orange found-take juice out of it and then drink- not hungry

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  • Iptables state tracking

    - by complexgeek
    Hi there. I've just taken over administration of a fairly complex firewall ruleset for a firewall box running Fedora Core 12, and there's one thing about it that is puzzling me. When I run nmap on the gateway from outside the network, I see all the expected services, but also sunrpc on port 111. The INPUT chain has DEFAULT DROP set, and there is no rule allowing port 111. As best I can tell (watching the packet counters before/during/after the scan) it's being allowed by the rule: "-m state --state RELATED,ESTABLISHED -j ACCEPT" but I don't understand why a brand new TCP connection would be considered RELATED or ESTABLISHED. Any suggestions would be greatly appreciated. EDIT: Conntrack modules: nf_conntrack_netlink 14925 0 nfnetlink 3479 1 nf_conntrack_netlink nf_conntrack_irc 5206 1 nf_nat_irc nf_conntrack_proto_udplite 3138 0 nf_conntrack_h323 62110 1 nf_nat_h323 nf_conntrack_proto_dccp 6878 0 nf_conntrack_sip 16921 1 nf_nat_sip nf_conntrack_proto_sctp 11131 0 nf_conntrack_pptp 10673 1 nf_nat_pptp nf_conntrack_sane 5458 0 nf_conntrack_proto_gre 6574 1 nf_conntrack_pptp nf_conntrack_amanda 2796 1 nf_nat_amanda nf_conntrack_ftp 11741 1 nf_nat_ftp nf_conntrack_tftp 4665 1 nf_nat_tftp nf_conntrack_netbios_ns 1534 0 nf_conntrack_ipv6 18504 2 ipv6 279399 40 ip6t_REJECT,nf_conntrack_ipv6 INPUT chain on the filter table: -A INPUT -s 192.168.200.10/32 -p tcp -m tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT -A INPUT -s 127.0.0.0/8 -i lo -j ACCEPT -A INPUT -p udp -m udp --sport 67:68 --dport 67:68 -j ACCEPT -A INPUT -d 192.168.200.5/32 -i eth0 -j ACCEPT -A INPUT -d 192.168.1.2/32 -i eth0 -j ACCEPT -A INPUT -d {public_ip}/32 -i ppp0 -p tcp -m multiport --dports 22,80,443 -j ACCEPT -A INPUT -d {public_ip}/32 -i ppp0 -p tcp -m multiport --sports 22,25,80,443 -j ACCEPT -A INPUT -d {public_ip}/32 -i ppp0 -p udp -m udp --dport 1194 -j ACCEPT -A INPUT -d {public_ip}/32 -i ppp0 -p udp -m udp --sport 1194 -j ACCEPT -A INPUT -d {public_ip}/32 -i ppp0 -p udp -m multiport --sports 53,123 -j ACCEPT -A INPUT -d {public_ip}/32 -i ppp0 -p icmp -m icmp --icmp-type 8 -j ACCEPT -A INPUT -i eth0 -m state --state NEW -j ACCEPT -A INPUT -d {public_ip}/32 -m state --state NEW -j ACCEPT -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT eth0 is connected to the internal network, eth3 is connected to an ADSL modem in bridge mode, ppp0 is the WAN connection tunneled over eth3.

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  • Copy / Move One SAP Client From One System to another System

    - by JonH
    We have one SAP system in the US (lets call it TKIJVPL1), this system has an SAP Client, client 241. We have another SAP system in Germany (lets call it Lockweiler). We need to move this client 241 from our TKIJVPL1 server to this new server. Can I simply use transaction SCC8? It says client export, but when I look at the options it says Source client : 241 (which is good), it says Profile Name SAP_ALL (which is also good as I need all data), but Target System all that is coming up is PL1 / QL1. What is the easiest way to export one client from one system to another system in SAP?

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  • Which Activator.CreateInstance overload function to call?

    - by user299990
    Which Activator.CreateInstance overload function to call? I have a type returned from "Type proxyType = GetProxyType(contractType);" and the constructorinfo is "[System.Reflection.RuntimeConstructorInfo] = {Void .ctor(System.ServiceModel.InstanceContext)} base {System.Reflection.MemberInfo} = {Void .ctor(System.ServiceModel.InstanceContext)} [System.Reflection.RuntimeConstructorInfo] = {Void .ctor(System.ServiceModel.InstanceContext, System.String)} base {System.Reflection.MethodBase} = {Void .ctor(System.ServiceModel.InstanceContext, System.String)} [System.Reflection.RuntimeConstructorInfo] = {Void .ctor(System.ServiceModel.InstanceContext, System.String, System.String)} base {System.Reflection.MethodBase} = {Void .ctor(System.ServiceModel.InstanceContext, System.String, System.String)} [System.Reflection.RuntimeConstructorInfo] = {Void .ctor(System.ServiceModel.InstanceContext, System.String, System.ServiceModel.EndpointAddress)} base {System.Reflection.MethodBase} = {Void .ctor(System.ServiceModel.InstanceContext, System.String, System.ServiceModel.EndpointAddress)} [System.Reflection.RuntimeConstructorInfo] = {Void .ctor(System.ServiceModel.InstanceContext, System.ServiceModel.Channels.Binding, System.ServiceModel.EndpointAddress)} base {System.Reflection.MethodBase} = {Void .ctor(System.ServiceModel.InstanceContext, System.ServiceModel.Channels.Binding, System.ServiceModel.EndpointAddress)}. Thanks!!

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  • File system query

    - by Balaji
    Is there an easy way to query data in file system? We are storing data in File system (instead of database) Is there a way to query the content of the file system? The data in the file system is stored in xml format. since the data is growing day by day we are finding it difficult to query the content of the files in the file system. Can anyone suggest what could be the tool/method to query the data in the existing file system?

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  • How do I create an encrypted file system inside a file?

    - by darent
    Recently i've found this interesting tutorial: http://flossstuff.wordpress.com/2011/08/07/using-a-file-as-a-storage-device/ It explains how to create an empty file, format it as ext4, and mount it as a device. I'd like to know if it can be created as an encrypted ext4 file system. I've tried using palimpsest (the disk utility found in System menu) to format the already created file system but it doesn't works as it detects the file system being used. If I try to unmount the file system, it won't work neither because it doesn't detect the device (since it's not a real device like a hardrive or a usb drive). So my question is, is there an option to create the file system encrypted from the begining? I've used these commands: Create an empty file 200Mb size: dd if=/dev/zero of=/path/to/file bs=1M count=200 Make it ext4: mkfs -t ext4 file Mount it in a folder inside my home: sudo mount -o loop file /path/to/mount_point Is there any way the mkfs command creates the ext4 encrypted asking for a decryption password? I'm planing to use this as a way to encrypt files inside Dropbox. Thanks for your time.

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  • Is there such thing as a "theory of system integration"?

    - by Jeff
    There is a plethora of different programs, servers, and in general technologies in use in organizations today. We, programmers, have lots of different tools at our disposal to help solve various different data, and communication challenges in an organization. Does anyone know if anyone has done an serious thinking about how systems are integrated? Let me give an example: Hypothetically, let's say I own a company that makes specialized suits a'la Iron Man. In the area of production, I have CAD tools, machining tools, payroll, project management, and asset management tools to name a few. I also have nice design space, where designers show off their designs on big displays, some touch, some traditional. Oh, and I also have one of these new fangled LEED Platinum buildings and it has number of different computer controlled systems, like smart window shutters that close when people are in the room, a HVAC system that adjusts depending on the number of people in the building, etc. What I want to know is if anyone has done any scientific work on trying to figure out how to hook all these pieces together, so that say my access control system is hooked to my payroll system, and my phone system allowing my never to swipe a time card, and to have my phone follow me throughout the building. This problem is also more than a technology challenge. Every technology implementation enables certain human behaviours, so the human must also be considered as a part of the system. Has anyone done any work in how effectively weave these components together? FYI: I am not trying to build a system. I want to know if anyone has thoroughly studied the process of doing a large integration project, how they develop their requirements, how they studied the human behaviors, etc.

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  • Win7 System folder contains infinitely looping SYSTEM(!) directory

    - by Matt
    My Windows 7 Enterprise computer has been crashing fairly frequently recently, so I decided to boot up in safe mode and run the TrendMicro client I have installed. It froze about 10 minutes into the full system scan, so in the spirit of http://whathaveyoutried.com, I started scanning each folder individually. When I got to ProgramData, the AV failed with an uncaught exception. I then went down a level and tried scanning Application Data, which failed as well. Imagine my surprise when I open the folder just to see the same folder again! As far as I can tell, this folder loop continues indefinitely. (If you are trying to recreate this, keep in mind that ProgramData is a hidden folder.) I'm actually a bit concerned that these are system folders, as this is a brand-new computer with a clean installation. I guess I have three questions: Has anyone else seen/experienced this before? I'm running Win7 SP1. How do I fix this? I've run CHKDSK \F with no success (although it was incredibly slow). What are the ramifications of an infinitely recursive directory? Theoretically speaking, each link takes up memory, so shouldn't I have no space available on my hard drive? (I've got about 180GB left.) I noticed that the tree view on the left only shows the "linked folder" icon on the deeper folders--does this mean anything special? (I've circled the icons or lack thereof in red.) How can the OS even resolve this aberration? And above all, what would happen if I were to select "Expand all folders"??? :P Matt

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  • System x3550 M2 stuck on system initializing after firmware upgrades

    - by itmanager223
    Hey guys so i have been having this major issue for the last few hours now. I have a system x 3550M2 server and i ran the UEFI and IMM firmware upgrades within windows server 2008 R2 x64. All upgrades went fine and i was told to reboot. I performed the reboot cleanly using the OS restart option. Upon restarting it showed the system initializing screen and it stayed there for a good hour. After that hour i figured it froze and so i powered down and power up again. Now i can not boot back up to even see the IBM splash screen or the OS... I have tried switching the Jumpers to go to the backup UEFI and backup IMM and no luck. I have also reset the CMOS power and i have pressed the reset button 3 times on the light path and no luck. There are no lights light on the light path to indicate anything is broken. The only thing i see on the light path is the number 0.5. Any ideas guys i am quite stumped with this problem. Thanks a lot, Dani Cela

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  • Is it possible that solid state drives (or any faster drive) will make common applications faster even if they are cached?

    - by leladax
    I assumed that solid state drives are insignificant after, say, Firefox is fully brought up and no important disk activity after that is going on. However, I wonder if some kind of 'cached from the disk to the CPU' activity is going on that may make solid state drives (or any faster drive) better. Then again, I suspect that may be depended only on the Bus (or some kind of cache memory drives have). Hrm..

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  • Understanding C# async / await (1) Compilation

    - by Dixin
    Now the async / await keywords are in C#. Just like the async and ! in F#, this new C# feature provides great convenience. There are many nice documents talking about how to use async / await in specific scenarios, like using async methods in ASP.NET 4.5 and in ASP.NET MVC 4, etc. In this article we will look at the real code working behind the syntax sugar. According to MSDN: The async modifier indicates that the method, lambda expression, or anonymous method that it modifies is asynchronous. Since lambda expression / anonymous method will be compiled to normal method, we will focus on normal async method. Preparation First of all, Some helper methods need to make up. internal class HelperMethods { internal static int Method(int arg0, int arg1) { // Do some IO. WebClient client = new WebClient(); Enumerable.Repeat("http://weblogs.asp.net/dixin", 10) .Select(client.DownloadString).ToArray(); int result = arg0 + arg1; return result; } internal static Task<int> MethodTask(int arg0, int arg1) { Task<int> task = new Task<int>(() => Method(arg0, arg1)); task.Start(); // Hot task (started task) should always be returned. return task; } internal static void Before() { } internal static void Continuation1(int arg) { } internal static void Continuation2(int arg) { } } Here Method() is a long running method doing some IO. Then MethodTask() wraps it into a Task and return that Task. Nothing special here. Await something in async method Since MethodTask() returns Task, let’s try to await it: internal class AsyncMethods { internal static async Task<int> MethodAsync(int arg0, int arg1) { int result = await HelperMethods.MethodTask(arg0, arg1); return result; } } Because we used await in the method, async must be put on the method. Now we get the first async method. According to the naming convenience, it is named MethodAsync. Of course a async method can be awaited. So we have a CallMethodAsync() to call MethodAsync(): internal class AsyncMethods { internal static async Task<int> CallMethodAsync(int arg0, int arg1) { int result = await MethodAsync(arg0, arg1); return result; } } After compilation, MethodAsync() and CallMethodAsync() becomes the same logic. This is the code of MethodAsyc(): internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MethodAsync(int arg0, int arg1) { MethodAsyncStateMachine methodAsyncStateMachine = new MethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; methodAsyncStateMachine.Builder.Start(ref methodAsyncStateMachine); return methodAsyncStateMachine.Builder.Task; } } It just creates and starts a state machine, MethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Result; private TaskAwaiter<int> awaitor; void IAsyncStateMachine.MoveNext() { try { if (this.State != 0) { this.awaitor = HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaitor.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaitor, ref this); return; } } else { this.State = -1; } this.Result = this.awaitor.GetResult(); } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); return; } this.State = -2; this.Builder.SetResult(this.Result); } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine param0) { this.Builder.SetStateMachine(param0); } } The generated code has been refactored, so it is readable and can be compiled. Several things can be observed here: The async modifier is gone, which shows, unlike other modifiers (e.g. static), there is no such IL/CLR level “async” stuff. It becomes a AsyncStateMachineAttribute. This is similar to the compilation of extension method. The generated state machine is very similar to the state machine of C# yield syntax sugar. The local variables (arg0, arg1, result) are compiled to fields of the state machine. The real code (await HelperMethods.MethodTask(arg0, arg1)) is compiled into MoveNext(): HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(). CallMethodAsync() will create and start its own state machine CallMethodAsyncStateMachine: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(CallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> CallMethodAsync(int arg0, int arg1) { CallMethodAsyncStateMachine callMethodAsyncStateMachine = new CallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; callMethodAsyncStateMachine.Builder.Start(ref callMethodAsyncStateMachine); return callMethodAsyncStateMachine.Builder.Task; } } CallMethodAsyncStateMachine has the same logic as MethodAsyncStateMachine above. The detail of the state machine will be discussed soon. Now it is clear that: async /await is a C# language level syntax sugar. There is no difference to await a async method or a normal method. As long as a method returns Task, it is awaitable. State machine and continuation To demonstrate more details in the state machine, a more complex method is created: internal class AsyncMethods { internal static async Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; } } In this method: There are multiple awaits. There are code before the awaits, and continuation code after each await After compilation, this multi-await method becomes the same as above single-await methods: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; multiCallMethodAsyncStateMachine.Builder.Start(ref multiCallMethodAsyncStateMachine); return multiCallMethodAsyncStateMachine.Builder.Task; } } It creates and starts one single state machine, MultiCallMethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Arg2; public int Arg3; public int ResultOfAwait1; public int ResultOfAwait2; public int ResultToReturn; private TaskAwaiter<int> awaiter; void IAsyncStateMachine.MoveNext() { try { switch (this.State) { case -1: HelperMethods.Before(); this.awaiter = AsyncMethods.MethodAsync(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 0: this.ResultOfAwait1 = this.awaiter.GetResult(); HelperMethods.Continuation1(this.ResultOfAwait1); this.awaiter = AsyncMethods.MethodAsync(this.Arg2, this.Arg3).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 1; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 1: this.ResultOfAwait2 = this.awaiter.GetResult(); HelperMethods.Continuation2(this.ResultOfAwait2); this.ResultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; this.State = -2; this.Builder.SetResult(this.ResultToReturn); break; } } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); } } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { this.Builder.SetStateMachine(stateMachine); } } Once again, the above state machine code is already refactored, but it still has a lot of things. More clean up can be done if we only keep the core logic, and the state machine can become very simple: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { // State: // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End public int State; public TaskCompletionSource<int> ResultToReturn; // int resultToReturn ... public int Arg0; // int Arg0 public int Arg1; // int arg1 public int Arg2; // int arg2 public int Arg3; // int arg3 public int ResultOfAwait1; // int resultOfAwait1 ... public int ResultOfAwait2; // int resultOfAwait2 ... private Task<int> currentTaskToAwait; /// <summary> /// Moves the state machine to its next state. /// </summary> public void MoveNext() // IAsyncStateMachine member. { try { switch (this.State) { // Original code is split by "await"s into "case"s: // case -1: // HelperMethods.Before(); // MethodAsync(Arg0, arg1); // case 0: // int resultOfAwait1 = await ... // HelperMethods.Continuation1(resultOfAwait1); // MethodAsync(arg2, arg3); // case 1: // int resultOfAwait2 = await ... // HelperMethods.Continuation2(resultOfAwait2); // int resultToReturn = resultOfAwait1 + resultOfAwait2; // return resultToReturn; case -1: // -1 is begin. HelperMethods.Before(); // Code before 1st await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg0, this.Arg1); // 1st task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 0. this.State = 0; MultiCallMethodAsyncStateMachine that1 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => that1.MoveNext()); break; case 0: // Now 1st await is done. this.ResultOfAwait1 = this.currentTaskToAwait.Result; // Get 1st await's result. HelperMethods.Continuation1(this.ResultOfAwait1); // Code after 1st await and before 2nd await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg2, this.Arg3); // 2nd task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 1. this.State = 1; MultiCallMethodAsyncStateMachine that2 = this; this.currentTaskToAwait.ContinueWith(_ => that2.MoveNext()); break; case 1: // Now 2nd await is done. this.ResultOfAwait2 = this.currentTaskToAwait.Result; // Get 2nd await's result. HelperMethods.Continuation2(this.ResultOfAwait2); // Code after 2nd await. int resultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; // Code after 2nd await. // End with resultToReturn. this.State = -2; // -2 is end. this.ResultToReturn.SetResult(resultToReturn); break; } } catch (Exception exception) { // End with exception. this.State = -2; // -2 is end. this.ResultToReturn.SetException(exception); } } /// <summary> /// Configures the state machine with a heap-allocated replica. /// </summary> /// <param name="stateMachine">The heap-allocated replica.</param> [DebuggerHidden] public void SetStateMachine(IAsyncStateMachine stateMachine) // IAsyncStateMachine member. { // No core logic. } } Only Task and TaskCompletionSource are involved in this version. And MultiCallMethodAsync() can be simplified to: [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, ResultToReturn = new TaskCompletionSource<int>(), // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End State = -1 }; multiCallMethodAsyncStateMachine.MoveNext(); // Original code are moved into this method. return multiCallMethodAsyncStateMachine.ResultToReturn.Task; } Now the whole state machine becomes very clean - it is about callback: Original code are split into pieces by “await”s, and each piece is put into each “case” in the state machine. Here the 2 awaits split the code into 3 pieces, so there are 3 “case”s. The “piece”s are chained by callback, that is done by Builder.AwaitUnsafeOnCompleted(callback), or currentTaskToAwait.ContinueWith(callback) in the simplified code. A previous “piece” will end with a Task (which is to be awaited), when the task is done, it will callback the next “piece”. The state machine’s state works with the “case”s to ensure the code “piece”s executes one after another. Callback If we focus on the point of callback, the simplification  can go even further – the entire state machine can be completely purged, and we can just keep the code inside MoveNext(). Now MultiCallMethodAsync() becomes: internal static Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { TaskCompletionSource<int> taskCompletionSource = new TaskCompletionSource<int>(); try { // Oringinal code begins. HelperMethods.Before(); MethodAsync(arg0, arg1).ContinueWith(await1 => { int resultOfAwait1 = await1.Result; HelperMethods.Continuation1(resultOfAwait1); MethodAsync(arg2, arg3).ContinueWith(await2 => { int resultOfAwait2 = await2.Result; HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; // Oringinal code ends. taskCompletionSource.SetResult(resultToReturn); }); }); } catch (Exception exception) { taskCompletionSource.SetException(exception); } return taskCompletionSource.Task; } Please compare with the original async / await code: HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; Yeah that is the magic of C# async / await: Await is not to wait. In a await expression, a Task object will be return immediately so that execution is not blocked. The continuation code is compiled as that Task’s callback code. When that task is done, continuation code will execute. Please notice that many details inside the state machine are omitted for simplicity, like context caring, etc. If you want to have a detailed picture, please do check out the source code of AsyncTaskMethodBuilder and TaskAwaiter.

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  • Creating Windows 8.1 system image error

    - by Random
    I'm experiencing "not enough space" error when trying to create system image to a USB hard drive: Detailed error: ERROR - A Volume Shadow Copy Service operation error has occurred: (0x8004231f) Insufficient storage available to create either the shadow copy storage file or other shadow copy data. Blah, blah... There is not enough disk space to create the volume shadow copy on the storage location. Make sure that, for all volumes to be backup up, the minimum required disk space for shadow copy creation is available. This applies to both the backup storage destination and volumes included in the backup. Minimum requirement: For volumes less than 500 megabytes, the minimum is 50 megabytes of free space. For volumes more than 500 megabytes, the minimum is 320 megabytes of free space. Recommended: At least 1 gigabyte of free disk space on each volume if volume size is more than 1 gigabyte. ERROR - A Volume Shadow Copy Service operation error has occurred: (0x8004231f) Insufficient storage available to create either the shadow copy storage file or other shadow copy data. I'd tried both - PowerShell wbAdmin start backup -backupTarget:E: -include:C: -allCritical -quiet and via Control Panel - File History button Clearly both EFI and Windows Recovery Environment partitions don't meet requirements coming from System Image tool (pic below) On top of that all system partitions are now shown as 100% free in Disk Management, it's disturbing but far from the actual state. My question is - hot to create System Image in Windows 8.1?

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  • System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host

    - by coffeeaddict
    We have 2 identical database tables on our dev server. In both is a table that holds an X509Certificate2 data in one of its fields. When I grab the cert along with the password that I've been using all along, it works over the first database just fine. I run the same code though over the 2nd database and get this error and I don't get why if the setup is exactly the same and the database is also on this server. So I'm not sure why when I switch my connection string to talk to Database2, even though it's setup the same and the code I'm running over it is the same, it complains. Here's the stack trace: An existing connection was forcibly closed by the remote host Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [SocketException (0x2746): An existing connection was forcibly closed by the remote host] System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size) +232 [IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.] System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size) +7035903 System.Net.FixedSizeReader.ReadPacket(Byte[] buffer, Int32 offset, Int32 count) +58 System.Net.Security.SslState.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest) +116 System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest) +123 System.Net.Security.SslState.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest) +86 System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest) +123 System.Net.Security.SslState.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest) +86 System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest) +123 System.Net.Security.SslState.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest) +86 System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest) +123 System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest) +7184357 System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult) +217 System.Threading.ExecutionContext.runTryCode(Object userData) +376 System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) +0 System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) +98 System.Net.TlsStream.ProcessAuthentication(LazyAsyncResult result) +1134 System.Net.TlsStream.Write(Byte[] buffer, Int32 offset, Int32 size) +88 System.Net.PooledStream.Write(Byte[] buffer, Int32 offset, Int32 size) +20 System.Net.ConnectStream.WriteHeaders(Boolean async) +360 [WebException: The underlying connection was closed: An unexpected error occurred on a send.] System.Web.Services.Protocols.WebClientProtocol.GetWebResponse(WebRequest request) +857631 System.Web.Services.Protocols.HttpWebClientProtocol.GetWebResponse(WebRequest request) +10 System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters) +243 Pmall.PayPal.PayPalApi.PayPalAPIAASoapBinding.SetExpressCheckout(SetExpressCheckoutReq SetExpressCheckoutReq) in C:\www\ssss\ssss\ssss\ssss\Reference.cs:1304 ssss.PayPal.ExpressCheckout.PayPalCheckout.SetExpressCheckout(PaymentDetailsType[] paymentDetails, String returnURL, String cancelURL, PayPalPaymentFlowType paymentFlowType) in C:\www\ssss\ssss\ssss\PayPalCheckout.cs:96 ssss.Web.ssss.SetExpressCheckout() in C:\www\ssss\ssss\ssss.aspx.cs:83 ssss.Web.ssss.Page_Load(Object sender, EventArgs e) in C:\www\ssss\ssss\Register.aspx.cs:24 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +42 System.Web.UI.Control.OnLoad(EventArgs e) +132 System.Web.UI.Control.LoadRecursive() +66 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2428

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  • Hotspot is getting disconnected from other windows system?

    - by Gaurav_Java
    I created Hotspot for sharing my system internet for other system . but after 5 - 10 min my system internet is not able to share internet but it is connected with other windows system .windows showing (No internet access ) But after running this sudo killall dnsmasq windows is able to use internet connection not happening with one system same thing is happening with 2 -3 windows system . In many cases i have 2 restart my system Here My Hotspot setting

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  • Unable to make the session state request to the session state server.

    - by Angry_IT_Guru
    For about 4-5 months now, I seem to be having this sporadic issue--mainly during our busiest time of the day between 10:30-11:45AM, where all my Windows 2003 web servers in a Microsoft NLB cluster start throwing session state server errors. A sample error is below. System.Web.HttpException: Unable to make the session state request to the session state server. Please ensure that the ASP.NET State service is started and that the client and server ports are the same. If the server is on a remote machine, please ensure that it accepts remote requests by checking the value of HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aspnet_state\Parameters\AllowRemoteConnection. If the server is on the local machine, and if the before mentioned registry value does not exist or is set to 0, then the state server connection string must use either 'localhost' or '127.0.0.1' as the server name. at System.Web.SessionState.OutOfProcSessionStateStore.MakeRequest(StateProtocolVerb verb, String id, StateProtocolExclusive exclusiveAccess, Int32 extraFlags, Int32 timeout, Int32 lockCookie, Byte[] buf, Int32 cb, Int32 networkTimeout, SessionNDMakeRequestResults& results) at System.Web.SessionState.OutOfProcSessionStateStore.SetAndReleaseItemExclusive(HttpContext context, String id, SessionStateStoreData item, Object lockId, Boolean newItem) at System.Web.SessionState.SessionStateModule.OnReleaseState(Object source, EventArgs eventArgs) at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) Now I'm using ASP.NET State service on a centralized back-end Windows 2003 server that all servers communicate to. I was originally using SQL Server state for a couple years as well prior to having this issue. The problem with SQL wqas that when the issue occurred, it created a blocking situation which essentially impacted all users across all servers. The product company recommended that I use the standard ASP.NET State service as that was what they technically supported. Why this would make a difference is beyond me -- but I had no choice but to try it! I have attempted to create multiple application pools, adding additional servers, chaning TCP/IP timeout from 20 to 30 seconds, and even calling Microsoft ASP.NET product support, with very little success. I even recommended that they review whether they are using read-only session state instead of read/write per page request -- as I understand that this basically causes every page to make round-trips to state server even if state isn't being used on the page. Unfortunately, the application is developed by our product company and they insist that it is something with my environment because other clients do not have these sort of issues. However, I've talked to other clients and they tell me when they've seen issues like they, they've basically had to create another web farm. This issue almost seems like I've simply reached some architectural limit within the application... Microsoft's position on the issue is that the session state needs to be reduced and the returncode being reported back from the state server indicates buffers are full. To better understand the scope of issues (rather than wait for customers to call and complain), I installed ELMAH and configured it to send me e-mails when unhandled exceptions occur. I basically get 500-1000 e-mails during the time period of high activity! If any one has any other ideas I could try or better ways to troubleshoot, I'd appreciate it.

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  • Resolving System Restore error - Error 0x800423F3 - The writer experienced a transient error

    - by Gishu
    System restore just stopped working, when I needed it most. (tried diff restore points... same error). Now everytime I run system-restore, it fails with the above error message. I cleared the event logs and retried to isolate the relevant events. I see 5 warnings and 1 info event from VSS and 1 error from System Restore. Here's the first warning from VSS and the error http://dl.dropbox.com/u/11733224/SystemRestore-FirstWarning.txt http://dl.dropbox.com/u/11733224/SystemRestore-FirstError.txt Tried a lot of stuff, but in vain; this error still persists.

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  • Resolving System Restore error - Error 0x800423F3 - The writer experienced a transient error

    - by Gishu
    System restore just stopped working, when I needed it most. (tried diff restore points... same error). Now everytime I run system-restore, it fails with the above error message. I cleared the event logs and retried to isolate the relevant events. I see 5 warnings and 1 info event from VSS and 1 error from System Restore. Here's the first warning from VSS and the error http://dl.dropbox.com/u/11733224/SystemRestore-FirstWarning.txt http://dl.dropbox.com/u/11733224/SystemRestore-FirstError.txt Tried a lot of stuff, but in vain; this error still persists.

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  • Recommendation on Ticket system with billing feature

    - by jacklty
    Actually, I do not know if I have used the right terms to describe our situation. Basically, We would like to have a system to help us to do billing and support at the same time. For example, we would like to offer outside users a customer support with ticket system, however the outside users need to purchase some credits beforehand through the system in order to submit their requests. Sometimes, our representatives will charge extra unit of credit for solving some open tickets due to the complexity and hours spent. (It will be nice to submit user a further billing request to same open ticket, and user can either accept/declined) Is there any available application or service we can use for the purpose above?

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  • XP Computer won't start (Missing/Corrupt 'System' file) - recently added new hard drive

    - by qwerty2
    Hi all, Pulling my hair out here. I recently replaced my D: 1TB drive (not a system drive) with a new 1.5TB drive. I loaded Windows XP, formatted the new drive and it was showing as working fine, alongside my C: windows system drive. I restart my machine and all of a sudden, Windows doesn't load and instead I get: "Windows could not start beause the following file is missing or corrupt" \WINDOWS\SYSTEM32\CONFIG\SYSTEM I don't have the original XP installation CD, although I do have another copy of XP, when I try and boot to it, I get the blue 'STOP' screen after it attempts to load the setup utlity for about a minute. Can someone please help? When I set up my new hard drive as a primary partition did this someone screw up my C: hard drive? Did it perhaps unmount it somehow? Any help would be fantastic. Thanks

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  • Windows System Recovery: Is it needed?

    - by starcorn
    Hello, I just recently deactivated system recovery on Vista, which saved me a huge amount of space. But I wonder is it necessary to have it activated? I can't remember that I any time had any use of system recovery anyway. And since it is Microsoft it probably would do a sloppy job anyway or? This question is for Windows XP, Vista, and 7. Do you have it activated? You can leave a comment if you have any opinion about the system recovery

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  • How to change the amount of RAM displayed in System Properties

    - by Nicu Zecheru
    I have this product that requires at least 1 GB Physical Memory in order to be installed. On my XP Pro machine I have 1 GB of RAM but in System Properties only 0.99 GB of RAM is displayed. The problem is that the product installer checks the memory displayed in System Properties (just a guess, not sure) and cannot continue the setup because it sees only 0.99 GB. Is there any way to change the displayed memory in the System Properties? Or how can I trick the installer to skip the memory check? Thanks.

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  • The best way to make full system dump on Centos [duplicate]

    - by tester3
    This question already has an answer here: Centos 5 Full backup 1 answer I am on Centos 6.5 with a lot of soft and services installed and working. Also I've got a lot of configs which damaged my brain and I dont want to do it again:) So, can anyone please advice the best way to make a full system dump with all data, so I need only to copy-paste them to new system to get my system ready on the other machine. Or something like that? P.S. Data on my hdd is encrypted, and I'd liked and encrypted dump too. Please help:)

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  • Running MySQL as SYSTEM Service in Windows XP

    - by enesviem
    I have this strange problem where I create a database in MySQL and I need to restart mysqld but I can't seem to do it with info the MySQL docs. Then, I kill it from the Task Manager and I can't restart it. When I look at the process, it is run by the SYSTEM, rather than me. When I run mysqld it starts the process by me, not the SYSTEM. Am I shutting it down incorrectly? IS there a way to start this daemon as the SYSTEM?

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