Updated to version 9.8.0

CryptoExchange.Net.Protobuf/CryptoExchange.Net.Protobuf.csproj

@@ -6,9 +6,9 @@
     <PackageId>CryptoExchange.Net.Protobuf</PackageId>
     <Authors>JKorf</Authors>
     <Description>Protobuf support for CryptoExchange.Net</Description>
-    <PackageVersion>9.6.0</PackageVersion>
-    <AssemblyVersion>9.6.0</AssemblyVersion>
-    <FileVersion>9.6.0</FileVersion>
+    <PackageVersion>9.8.0</PackageVersion>
+    <AssemblyVersion>9.8.0</AssemblyVersion>
+    <FileVersion>9.8.0</FileVersion>
     <PackageRequireLicenseAcceptance>false</PackageRequireLicenseAcceptance>
     <PackageTags>CryptoExchange;CryptoExchange.Net</PackageTags>
     <RepositoryType>git</RepositoryType>
@@ -41,7 +41,7 @@
     <DocumentationFile>CryptoExchange.Net.Protobuf.xml</DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="CryptoExchange.Net" Version="9.6.0" />
+    <PackageReference Include="CryptoExchange.Net" Version="9.8.0" />
     <PackageReference Include="protobuf-net" Version="3.2.56" />
   </ItemGroup>
 </Project>

CryptoExchange.Net.Protobuf/README.md

@@ -5,6 +5,12 @@
 Protobuf support for CryptoExchange.Net.
 
 ## Release notes
+* Version 9.8.0 - 30 Sep 2025
+    * Updated CryptoExchange.Net version to 9.8.0, see https://github.com/JKorf/CryptoExchange.Net/releases/
+
+* Version 9.7.0 - 01 Sep 2025
+    * Updated CryptoExchange.Net version to 9.7.0, see https://github.com/JKorf/CryptoExchange.Net/releases/
+
 * Version 9.6.0 - 25 Aug 2025
     * Updated CryptoExchange.Net version to 9.6.0
 

CryptoExchange.Net.UnitTests/ExchangeHelpersTests.cs

@@ -32,6 +32,7 @@ namespace CryptoExchange.Net.UnitTests
         [TestCase(0.1, 1, 0.0001, RoundingType.Closest, 0.532, 0.532)]
         [TestCase(0.1, 1, 0.0001, RoundingType.Down, 0.5516592, 0.5516)]
         [TestCase(0.1, 1, 0.0001, RoundingType.Closest, 0.5516592, 0.5517)]
+        [TestCase(0, 1, 0.000000001, RoundingType.Closest, 0.0000097232, 0.000009723)]
         public void AdjustValueStepTests(decimal min, decimal max, decimal? step, RoundingType roundingType, decimal input, decimal expected)
         {
             var result = ExchangeHelpers.AdjustValueStep(min, max, step, roundingType, input);

CryptoExchange.Net/Clients/SocketApiClient.cs

@@ -227,7 +227,7 @@ namespace CryptoExchange.Net.Clients
                 while (true)
                 {
                     // Get a new or existing socket connection
-                    var socketResult = await GetSocketConnection(url, subscription.Authenticated, false, subscription.Topic).ConfigureAwait(false);
+                    var socketResult = await GetSocketConnection(url, subscription.Authenticated, false, ct, subscription.Topic).ConfigureAwait(false);
                     if (!socketResult)
                         return socketResult.As<UpdateSubscription>(null);
 
@@ -343,7 +343,7 @@ namespace CryptoExchange.Net.Clients
             await semaphoreSlim.WaitAsync().ConfigureAwait(false);
             try
             {
-                var socketResult = await GetSocketConnection(url, query.Authenticated, true).ConfigureAwait(false);
+                var socketResult = await GetSocketConnection(url, query.Authenticated, true, ct).ConfigureAwait(false);
                 if (!socketResult)
                     return socketResult.As<THandlerResponse>(default);
 
@@ -494,25 +494,56 @@ namespace CryptoExchange.Net.Clients
         /// <param name="address">The address the socket is for</param>
         /// <param name="authenticated">Whether the socket should be authenticated</param>
         /// <param name="dedicatedRequestConnection">Whether a dedicated request connection should be returned</param>
+        /// <param name="ct">Cancellation token</param>
         /// <param name="topic">The subscription topic, can be provided when multiple of the same topics are not allowed on a connection</param>
         /// <returns></returns>
-        protected virtual async Task<CallResult<SocketConnection>> GetSocketConnection(string address, bool authenticated, bool dedicatedRequestConnection, string? topic = null)
+        protected virtual async Task<CallResult<SocketConnection>> GetSocketConnection(string address, bool authenticated, bool dedicatedRequestConnection, CancellationToken ct, string? topic = null)
         {
-            var socketQuery = socketConnections.Where(s => (s.Value.Status == SocketConnection.SocketStatus.None || s.Value.Status == SocketConnection.SocketStatus.Connected)
-                                                      && s.Value.Tag.TrimEnd('/') == address.TrimEnd('/')
+            var socketQuery = socketConnections.Where(s => s.Value.Tag.TrimEnd('/') == address.TrimEnd('/')
                                                       && s.Value.ApiClient.GetType() == GetType()
-                                                      && (s.Value.Authenticated == authenticated || !authenticated)
-                                                      && (AllowTopicsOnTheSameConnection || !s.Value.Topics.Contains(topic))
-                                                      && s.Value.Connected);
+                                                      && (AllowTopicsOnTheSameConnection || !s.Value.Topics.Contains(topic)))
+                                                .Select(x => x.Value)
+                                                .ToList();
 
-            SocketConnection connection;
+            // If all current socket connections are reconnecting or resubscribing wait for that to finish as we can probably use the existing connection
+            var delayStart = DateTime.UtcNow;
+            var delayed = false;
+            while (socketQuery.Count >= 1 && socketQuery.All(x => x.Status == SocketConnection.SocketStatus.Reconnecting || x.Status == SocketConnection.SocketStatus.Resubscribing))
+            {
+                if (DateTime.UtcNow - delayStart > TimeSpan.FromSeconds(10))
+                {
+                    if (socketQuery.Count >= 1 && socketQuery.All(x => x.Status == SocketConnection.SocketStatus.Reconnecting || x.Status == SocketConnection.SocketStatus.Resubscribing))
+                    {
+                        // If after this time we still trying to reconnect/reprocess there is some issue in the connection
+                        _logger.TimeoutWaitingForReconnectingSocket();
+                        return new CallResult<SocketConnection>(new CantConnectError());
+                    }
+
+                    break;
+                }
+
+                delayed = true;
+                try { await Task.Delay(50, ct).ConfigureAwait(false); } catch (Exception) { }
+
+                if (ct.IsCancellationRequested)
+                    return new CallResult<SocketConnection>(new CancellationRequestedError());
+            }
+
+            if (delayed)
+                _logger.WaitedForReconnectingSocket((long)(DateTime.UtcNow - delayStart).TotalMilliseconds);
+
+            socketQuery = socketQuery.Where(s => (s.Status == SocketConnection.SocketStatus.None || s.Status == SocketConnection.SocketStatus.Connected)                                                     
+                                                && (s.Authenticated == authenticated || !authenticated)
+                                                && s.Connected).ToList();
+
+            SocketConnection? connection;
             if (!dedicatedRequestConnection)
             {
-                connection = socketQuery.Where(s => !s.Value.DedicatedRequestConnection.IsDedicatedRequestConnection).OrderBy(s => s.Value.UserSubscriptionCount).FirstOrDefault().Value;
+                connection = socketQuery.Where(s => !s.DedicatedRequestConnection.IsDedicatedRequestConnection).OrderBy(s => s.UserSubscriptionCount).FirstOrDefault();
             }
             else
             {
-                connection = socketQuery.Where(s => s.Value.DedicatedRequestConnection.IsDedicatedRequestConnection).FirstOrDefault().Value;
+                connection = socketQuery.Where(s => s.DedicatedRequestConnection.IsDedicatedRequestConnection).FirstOrDefault();
                 if (connection != null && !connection.DedicatedRequestConnection.Authenticated)
                     // Mark dedicated request connection as authenticated if the request is authenticated
                     connection.DedicatedRequestConnection.Authenticated = authenticated;
@@ -520,9 +551,12 @@ namespace CryptoExchange.Net.Clients
 
             if (connection != null)
             {
-                if (connection.UserSubscriptionCount < ClientOptions.SocketSubscriptionsCombineTarget || (socketConnections.Count >= (ApiOptions.MaxSocketConnections ?? ClientOptions.MaxSocketConnections) && socketConnections.All(s => s.Value.UserSubscriptionCount >= ClientOptions.SocketSubscriptionsCombineTarget)))
+                if (connection.UserSubscriptionCount < ClientOptions.SocketSubscriptionsCombineTarget
+                    || (socketConnections.Count >= (ApiOptions.MaxSocketConnections ?? ClientOptions.MaxSocketConnections) && socketConnections.All(s => s.Value.UserSubscriptionCount >= ClientOptions.SocketSubscriptionsCombineTarget)))
+                {
                     // Use existing socket if it has less than target connections OR it has the least connections and we can't make new
                     return new CallResult<SocketConnection>(connection);
+                }
             }
 
             var connectionAddress = await GetConnectionUrlAsync(address, authenticated).ConfigureAwait(false);
@@ -716,7 +750,7 @@ namespace CryptoExchange.Net.Clients
         {
             foreach (var item in DedicatedConnectionConfigs)
             {
-                var socketResult = await GetSocketConnection(item.SocketAddress, item.Authenticated, true).ConfigureAwait(false);
+                var socketResult = await GetSocketConnection(item.SocketAddress, item.Authenticated, true, CancellationToken.None).ConfigureAwait(false);
                 if (!socketResult)
                     return socketResult.AsDataless();
 

CryptoExchange.Net/Converters/SystemTextJson/EnumConverter.cs

@@ -140,10 +140,10 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
                 _ => throw new Exception("Invalid token type for enum deserialization: " + reader.TokenType)
             };
 
-            if (string.IsNullOrEmpty(stringValue))
+            if (stringValue is null)
                 return null;
 
-            if (!GetValue(enumType, stringValue!, out var result))
+            if (!GetValue(enumType, stringValue, out var result))
             {
                 if (string.IsNullOrWhiteSpace(stringValue))
                 {
@@ -204,6 +204,13 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
                 return false;
             }
 
+            if (String.IsNullOrEmpty(value))
+            {
+                // An empty/null value will always fail when parsing, so just return here
+                result = default;
+                return false;
+            }
+
             try
             {
                 // If no explicit mapping is found try to parse string

CryptoExchange.Net/CryptoExchange.Net.csproj

@@ -6,9 +6,9 @@
     <PackageId>CryptoExchange.Net</PackageId>
     <Authors>JKorf</Authors>
     <Description>CryptoExchange.Net is a base library which is used to implement different cryptocurrency (exchange) API's. It provides a standardized way of implementing different API's, which results in a very similar experience for users of the API implementations.</Description>
-    <PackageVersion>9.7.0</PackageVersion>
-    <AssemblyVersion>9.7.0</AssemblyVersion>
-    <FileVersion>9.7.0</FileVersion>
+    <PackageVersion>9.8.0</PackageVersion>
+    <AssemblyVersion>9.8.0</AssemblyVersion>
+    <FileVersion>9.8.0</FileVersion>
     <PackageRequireLicenseAcceptance>false</PackageRequireLicenseAcceptance>
     <PackageTags>OKX;OKX.Net;Mexc;Mexc.Net;Kucoin;Kucoin.Net;Kraken;Kraken.Net;Huobi;Huobi.Net;CoinEx;CoinEx.Net;Bybit;Bybit.Net;Bitget;Bitget.Net;Bitfinex;Bitfinex.Net;Binance;Binance.Net;CryptoCurrency;CryptoCurrency Exchange;CryptoExchange.Net</PackageTags>
     <RepositoryType>git</RepositoryType>

CryptoExchange.Net/ExchangeHelpers.cs

@@ -88,8 +88,6 @@ namespace CryptoExchange.Net
                     value -= offset;
                 else value += (step.Value - offset);
             }
-
-            value = RoundDown(value, 8);
                 
             return value.Normalize();
         }

CryptoExchange.Net/Interfaces/ITrackerFactory.cs

@@ -0,0 +1,45 @@
+using CryptoExchange.Net.SharedApis;
+using CryptoExchange.Net.Trackers.Klines;
+using CryptoExchange.Net.Trackers.Trades;
+using System;
+
+namespace CryptoExchange.Net.Interfaces
+{
+    /// <summary>
+    /// Tracker factory
+    /// </summary>
+    public interface ITrackerFactory
+    {
+        /// <summary>
+        /// Whether the factory supports creating a KlineTracker instance for this symbol and interval
+        /// </summary>
+        /// <param name="symbol">The symbol</param>
+        /// <param name="interval">The kline interval</param>
+        bool CanCreateKlineTracker(SharedSymbol symbol, SharedKlineInterval interval);
+
+        /// <summary>
+        /// Create a new kline tracker
+        /// </summary>
+        /// <param name="symbol">The symbol</param>
+        /// <param name="interval">Kline interval</param>
+        /// <param name="limit">The max amount of klines to retain</param>
+        /// <param name="period">The max period the data should be retained</param>
+        /// <returns></returns>
+        IKlineTracker CreateKlineTracker(SharedSymbol symbol, SharedKlineInterval interval, int? limit = null, TimeSpan? period = null);
+
+        /// <summary>
+        /// Whether the factory supports creating a TradeTracker instance for this symbol
+        /// </summary>
+        /// <param name="symbol">The symbol</param>
+        bool CanCreateTradeTracker(SharedSymbol symbol);
+
+        /// <summary>
+        /// Create a new trade tracker for a symbol
+        /// </summary>
+        /// <param name="symbol">The symbol</param>
+        /// <param name="limit">The max amount of trades to retain</param>
+        /// <param name="period">The max period the data should be retained</param>
+        /// <returns></returns>
+        ITradeTracker CreateTradeTracker(SharedSymbol symbol, int? limit = null, TimeSpan? period = null);
+    }
+}

CryptoExchange.Net/Logging/Extensions/SocketApiClientLoggingExtension.cs

@@ -23,6 +23,8 @@ namespace CryptoExchange.Net.Logging.Extensions
         private static readonly Action<ILogger, int, int, Exception?> _unsubscribingSubscription;
         private static readonly Action<ILogger, int, Exception?> _reconnectingAllConnections;
         private static readonly Action<ILogger, DateTime, Exception?> _addingRetryAfterGuard;
+        private static readonly Action<ILogger, Exception?> _timeoutWaitingForReconnectingSocket;
+        private static readonly Action<ILogger, long, Exception?> _waitedForReconnectingSocket;
 
         static SocketApiClientLoggingExtension()
         {
@@ -110,6 +112,16 @@ namespace CryptoExchange.Net.Logging.Extensions
                 LogLevel.Warning,
                 new EventId(3018, "AddRetryAfterGuard"),
                 "Adding RetryAfterGuard ({RetryAfter}) because the connection attempt was rate limited");
+
+            _timeoutWaitingForReconnectingSocket = LoggerMessage.Define(
+                LogLevel.Debug,
+                new EventId(3019, "TimeoutWaitingForReconnectingSocket"),
+                "Timeout while waiting for existing socket reconnection, failing request");
+
+            _waitedForReconnectingSocket = LoggerMessage.Define<long>(
+                LogLevel.Trace,
+                new EventId(3020, "WaitedForReconnectingSocket"),
+                "Waited for reconnecting socket for {Timespan}ms");
         }
 
         public static void FailedToAddSubscriptionRetryOnDifferentConnection(this ILogger logger, int socketId)
@@ -196,5 +208,14 @@ namespace CryptoExchange.Net.Logging.Extensions
         {
             _addingRetryAfterGuard(logger, retryAfter, null);
         }
+
+        public static void TimeoutWaitingForReconnectingSocket(this ILogger logger)
+        {
+            _timeoutWaitingForReconnectingSocket(logger, null);
+        }
+        public static void WaitedForReconnectingSocket(this ILogger logger, long milliseconds)
+        {
+            _waitedForReconnectingSocket(logger, milliseconds, null);
+        }
     }
 }

CryptoExchange.Net/Objects/Sockets/UpdateSubscription.cs

@@ -1,5 +1,7 @@
 using CryptoExchange.Net.Sockets;
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
 
 namespace CryptoExchange.Net.Objects.Sockets
@@ -12,13 +14,21 @@ namespace CryptoExchange.Net.Objects.Sockets
         private readonly SocketConnection _connection;
         private readonly Subscription _listener;
 
+        private object _eventLock = new object();
+        private List<Action> _connectionClosedEventHandlers = new List<Action>();
+        private List<Action> _connectionLostEventHandlers = new List<Action>();
+        private List<Action<Error>> _resubscribeFailedEventHandlers = new List<Action<Error>>();
+        private List<Action<TimeSpan>> _connectionRestoredEventHandlers = new List<Action<TimeSpan>>();
+        private List<Action> _activityPausedEventHandlers = new List<Action>();
+        private List<Action> _activityUnpausedEventHandlers = new List<Action>();
+
         /// <summary>
         /// Event when the connection is lost. The socket will automatically reconnect when possible.
         /// </summary>
         public event Action ConnectionLost
         {
-            add => _connection.ConnectionLost += value;
-            remove => _connection.ConnectionLost -= value;
+            add { lock (_eventLock) _connectionLostEventHandlers.Add(value); }
+            remove { lock (_eventLock) _connectionLostEventHandlers.Remove(value); }
         }
 
         /// <summary>
@@ -26,8 +36,8 @@ namespace CryptoExchange.Net.Objects.Sockets
         /// </summary>
         public event Action ConnectionClosed
         {
-            add => _connection.ConnectionClosed += value;
-            remove => _connection.ConnectionClosed -= value;
+            add { lock (_eventLock) _connectionClosedEventHandlers.Add(value); }
+            remove { lock (_eventLock) _connectionClosedEventHandlers.Remove(value); }
         }
 
         /// <summary>
@@ -35,8 +45,8 @@ namespace CryptoExchange.Net.Objects.Sockets
         /// </summary>
         public event Action<Error> ResubscribingFailed
         {
-            add => _connection.ResubscribingFailed += value;
-            remove => _connection.ResubscribingFailed -= value;
+            add { lock (_eventLock) _resubscribeFailedEventHandlers.Add(value); }
+            remove { lock (_eventLock) _resubscribeFailedEventHandlers.Remove(value); }
         }
 
         /// <summary>
@@ -46,8 +56,8 @@ namespace CryptoExchange.Net.Objects.Sockets
         /// </summary>
         public event Action<TimeSpan> ConnectionRestored
         {
-            add => _connection.ConnectionRestored += value;
-            remove => _connection.ConnectionRestored -= value;
+            add { lock (_eventLock) _connectionRestoredEventHandlers.Add(value); }
+            remove { lock (_eventLock) _connectionRestoredEventHandlers.Remove(value); }
         }
 
         /// <summary>
@@ -55,8 +65,8 @@ namespace CryptoExchange.Net.Objects.Sockets
         /// </summary>
         public event Action ActivityPaused
         {
-            add => _connection.ActivityPaused += value;
-            remove => _connection.ActivityPaused -= value;
+            add { lock (_eventLock) _activityPausedEventHandlers.Add(value); }
+            remove { lock (_eventLock) _activityPausedEventHandlers.Remove(value); }
         }
 
         /// <summary>
@@ -64,8 +74,8 @@ namespace CryptoExchange.Net.Objects.Sockets
         /// </summary>
         public event Action ActivityUnpaused
         {
-            add => _connection.ActivityUnpaused += value;
-            remove => _connection.ActivityUnpaused -= value;
+            add { lock (_eventLock) _activityUnpausedEventHandlers.Add(value); }
+            remove { lock (_eventLock) _activityUnpausedEventHandlers.Remove(value); }
         }
 
         /// <summary>
@@ -95,7 +105,85 @@ namespace CryptoExchange.Net.Objects.Sockets
         public UpdateSubscription(SocketConnection connection, Subscription subscription)
         {
             _connection = connection;
+            _connection.ConnectionClosed += HandleConnectionClosedEvent;
+            _connection.ConnectionLost += HandleConnectionLostEvent;
+            _connection.ConnectionRestored += HandleConnectionRestoredEvent;
+            _connection.ResubscribingFailed += HandleResubscribeFailedEvent;
+            _connection.ActivityPaused += HandlePausedEvent;
+            _connection.ActivityUnpaused += HandleUnpausedEvent;
+
             _listener = subscription;
+            _listener.Unsubscribed += HandleUnsubscribed;
+        }
+
+        private void HandleUnsubscribed()
+        {
+            _connection.ConnectionClosed -= HandleConnectionClosedEvent;
+            _connection.ConnectionLost -= HandleConnectionLostEvent;
+            _connection.ConnectionRestored -= HandleConnectionRestoredEvent;
+            _connection.ResubscribingFailed -= HandleResubscribeFailedEvent;
+            _connection.ActivityPaused -= HandlePausedEvent;
+            _connection.ActivityUnpaused -= HandleUnpausedEvent;
+        }
+
+        private void HandleConnectionClosedEvent()
+        {
+            List<Action> handlers;
+            lock (_eventLock)
+                handlers = _connectionClosedEventHandlers.ToList();
+
+            foreach(var callback in handlers)
+                callback();
+        }
+
+        private void HandleConnectionLostEvent()
+        {
+            List<Action> handlers;
+            lock (_eventLock)
+                handlers = _connectionLostEventHandlers.ToList();
+
+            foreach (var callback in handlers)
+                callback();
+        }
+
+        private void HandleConnectionRestoredEvent(TimeSpan period)
+        {
+            List<Action<TimeSpan>> handlers;
+            lock (_eventLock)
+                handlers = _connectionRestoredEventHandlers.ToList();
+
+            foreach (var callback in handlers)
+                callback(period);
+        }
+
+        private void HandleResubscribeFailedEvent(Error error)
+        {
+            List<Action<Error>> handlers;
+            lock (_eventLock)
+                handlers = _resubscribeFailedEventHandlers.ToList();
+
+            foreach (var callback in handlers)
+                callback(error);
+        }
+
+        private void HandlePausedEvent()
+        {
+            List<Action> handlers;
+            lock (_eventLock)
+                handlers = _activityPausedEventHandlers.ToList();
+
+            foreach (var callback in handlers)
+                callback();
+        }
+
+        private void HandleUnpausedEvent()
+        {
+            List<Action> handlers;
+            lock (_eventLock)
+                handlers = _activityUnpausedEventHandlers.ToList();
+
+            foreach (var callback in handlers)
+                callback();
         }
 
         /// <summary>

CryptoExchange.Net/SharedApis/ResponseModels/SharedAsset.cs

@@ -67,6 +67,10 @@ namespace CryptoExchange.Net.SharedApis
         /// Min number of confirmations
         /// </summary>
         public int? MinConfirmations { get; set; }
+        /// <summary>
+        /// The contract address
+        /// </summary>
+        public string? ContractAddress { get; set; }
 
         /// <summary>
         /// ctor

CryptoExchange.Net/Sockets/SocketConnection.cs

@@ -706,6 +706,8 @@ namespace CryptoExchange.Net.Sockets
 
             lock (_listenersLock)
                 _listeners.Remove(subscription);
+
+            subscription.InvokeUnsubscribedHandler();
         }
 
         /// <summary>

CryptoExchange.Net/Sockets/Subscription.cs

@@ -74,6 +74,10 @@ namespace CryptoExchange.Net.Sockets
         /// Exception event
         /// </summary>
         public event Action<Exception>? Exception;
+        /// <summary>
+        /// Listener unsubscribed event
+        /// </summary>
+        public event Action? Unsubscribed;
 
         /// <summary>
         /// Subscription topic
@@ -181,6 +185,14 @@ namespace CryptoExchange.Net.Sockets
             Exception?.Invoke(e);
         }
 
+        /// <summary>
+        /// Invoke the unsubscribed event
+        /// </summary>
+        public void InvokeUnsubscribedHandler()
+        {
+            Unsubscribed?.Invoke();
+        }
+
         /// <summary>
         /// State of this subscription
         /// </summary>

Examples/BlazorClient/BlazorClient.csproj

@@ -5,29 +5,30 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Binance.Net" Version="11.3.0" />
-    <PackageReference Include="Bitfinex.Net" Version="9.3.0" />
-    <PackageReference Include="BitMart.Net" Version="2.4.1" />
-    <PackageReference Include="Bybit.Net" Version="5.4.0" />
-    <PackageReference Include="CoinEx.Net" Version="9.3.0" />
-    <PackageReference Include="CoinW.Net" Version="1.0.1" />
-    <PackageReference Include="CryptoCom.Net" Version="2.4.0" />
-    <PackageReference Include="DeepCoin.Net" Version="2.3.0" />
-    <PackageReference Include="GateIo.Net" Version="2.4.0" />
-    <PackageReference Include="HyperLiquid.Net" Version="2.4.0" />
-    <PackageReference Include="JK.BingX.Net" Version="2.3.0" />
-    <PackageReference Include="JK.Bitget.Net" Version="2.3.0" />
-    <PackageReference Include="JK.Mexc.Net" Version="3.3.0" />
-    <PackageReference Include="JK.OKX.Net" Version="3.3.1" />
-    <PackageReference Include="JKorf.BitMEX.Net" Version="2.3.0" />
-    <PackageReference Include="JKorf.Coinbase.Net" Version="2.3.0" />
-    <PackageReference Include="JKorf.HTX.Net" Version="7.3.0" />
-    <PackageReference Include="KrakenExchange.Net" Version="6.3.1" />
-    <PackageReference Include="Kucoin.Net" Version="7.3.0" />
+    <PackageReference Include="Binance.Net" Version="11.7.1" />
+    <PackageReference Include="Bitfinex.Net" Version="9.7.0" />
+    <PackageReference Include="BitMart.Net" Version="2.8.0" />
+    <PackageReference Include="BloFin.Net" Version="1.0.0" />
+    <PackageReference Include="Bybit.Net" Version="5.8.0" />
+    <PackageReference Include="CoinEx.Net" Version="9.7.0" />
+    <PackageReference Include="CoinW.Net" Version="1.4.0" />
+    <PackageReference Include="CryptoCom.Net" Version="2.8.0" />
+    <PackageReference Include="DeepCoin.Net" Version="2.7.0" />
+    <PackageReference Include="GateIo.Net" Version="2.8.1" />
+    <PackageReference Include="HyperLiquid.Net" Version="2.12.0" />
+    <PackageReference Include="JK.BingX.Net" Version="2.7.0" />
+    <PackageReference Include="JK.Bitget.Net" Version="2.7.1" />
+    <PackageReference Include="JK.Mexc.Net" Version="3.8.0" />
+    <PackageReference Include="JK.OKX.Net" Version="3.7.1" />
+    <PackageReference Include="JKorf.BitMEX.Net" Version="2.7.0" />
+    <PackageReference Include="JKorf.Coinbase.Net" Version="2.7.0" />
+    <PackageReference Include="JKorf.HTX.Net" Version="7.7.0" />
+    <PackageReference Include="KrakenExchange.Net" Version="6.7.0" />
+    <PackageReference Include="Kucoin.Net" Version="7.7.1" />
     <PackageReference Include="Serilog.AspNetCore" Version="9.0.0" />
-    <PackageReference Include="Toobit.Net" Version="1.2.1" />
-    <PackageReference Include="WhiteBit.Net" Version="2.4.0" />
-    <PackageReference Include="XT.Net" Version="2.3.1" />
+    <PackageReference Include="Toobit.Net" Version="1.6.0" />
+    <PackageReference Include="WhiteBit.Net" Version="2.8.0" />
+    <PackageReference Include="XT.Net" Version="2.7.0" />
   </ItemGroup>
 
 </Project>

Examples/BlazorClient/Pages/Index.razor

@@ -5,6 +5,7 @@
 @inject IBitgetRestClient bitgetClient
 @inject IBitMartRestClient bitmartClient
 @inject IBitMEXRestClient bitmexClient
+@inject IBloFinRestClient bloFinClient
 @inject IBybitRestClient bybitClient
 @inject ICoinbaseRestClient coinbaseClient
 @inject ICoinExRestClient coinexClient
@@ -39,6 +40,7 @@
         var bitgetTask = bitgetClient.SpotApiV2.ExchangeData.GetTickersAsync("BTCUSDT");
         var bitmartTask = bitmartClient.SpotApi.ExchangeData.GetTickerAsync("BTC_USDT");
         var bitmexTask = bitmexClient.ExchangeApi.ExchangeData.GetSymbolsAsync("XBT_USDT");
+        var bloFinTask = bloFinClient.FuturesApi.ExchangeData.GetTickersAsync("BTC-USDT");
         var bybitTask = bybitClient.V5Api.ExchangeData.GetSpotTickersAsync("BTCUSDT");
         var coinbaseTask = coinbaseClient.AdvancedTradeApi.ExchangeData.GetSymbolAsync("BTC-USDT");
         var coinexTask = coinexClient.SpotApiV2.ExchangeData.GetTickersAsync(["BTCUSDT"]);
@@ -76,6 +78,9 @@
         if (bitmexTask.Result.Success)
             _prices.Add("BitMEX", bitmexTask.Result.Data.First().LastPrice);
 
+        if (bloFinTask.Result.Success)
+            _prices.Add("BloFin", bloFinTask.Result.Data.First().LastPrice);
+
         if (bybitTask.Result.Success)
             _prices.Add("Bybit", bybitTask.Result.Data.List.First().LastPrice);
 

Examples/BlazorClient/Pages/LiveData.razor

@@ -5,6 +5,7 @@
 @inject IBitgetSocketClient bitgetSocketClient
 @inject IBitMartSocketClient bitmartSocketClient
 @inject IBitMEXSocketClient bitmexSocketClient
+@inject IBloFinSocketClient bloFinSocketClient
 @inject IBybitSocketClient bybitSocketClient
 @inject ICoinbaseSocketClient coinbaseSocketClient
 @inject ICoinExSocketClient coinExSocketClient
@@ -48,6 +49,8 @@
             bitgetSocketClient.SpotApiV2.SubscribeToTickerUpdatesAsync("ETHBTC", data => UpdateData("Bitget", data.Data.LastPrice)),
             bitmartSocketClient.SpotApi.SubscribeToTickerUpdatesAsync("ETH_BTC", data => UpdateData("BitMart", data.Data.LastPrice)),
             bitmexSocketClient.ExchangeApi.SubscribeToSymbolUpdatesAsync("ETH_XBT", data => UpdateData("BitMEX", data.Data.LastPrice ?? 0)),
+            // BloFin doesn't support the ETH/BTC pair
+            //bloFinSocketClient.FuturesApi.SubscribeToTickerUpdatesAsync("ETH-BTC", data => UpdateData("BloFin", data.Data.LastPrice)),
             bybitSocketClient.V5SpotApi.SubscribeToTickerUpdatesAsync("ETHBTC", data => UpdateData("Bybit", data.Data.LastPrice)),
             coinExSocketClient.SpotApiV2.SubscribeToTickerUpdatesAsync(["ETHBTC"], data => UpdateData("CoinEx", data.Data.First().LastPrice)),
             coinWSocketClient.SpotApi.SubscribeToTickerUpdatesAsync("ETH_BTC", data => UpdateData("CoinW", data.Data.LastPrice)),
@@ -61,7 +64,8 @@
             //hyperLiquidSocketClient.SpotApi.SubscribeToSymbolUpdatesAsync("ETH", data => UpdateData("HyperLiquid", data.Data.MidPrice ?? 0)),
             krakenSocketClient.SpotApi.SubscribeToTickerUpdatesAsync("ETH/BTC", data => UpdateData("Kraken", data.Data.LastPrice)),
             kucoinSocketClient.SpotApi.SubscribeToTickerUpdatesAsync("ETH-BTC", data => UpdateData("Kucoin", data.Data.LastPrice ?? 0)),
-            mexcSocketClient.SpotApi.SubscribeToMiniTickerUpdatesAsync("ETHBTC", data => UpdateData("Mexc", data.Data.LastPrice)),
+            // Mexc doesn't offer a ticker stream currently
+            //mexcSocketClient.SpotApi.SubscribeToMiniTickerUpdatesAsync("ETHBTC", data => UpdateData("Mexc", data.Data.LastPrice)),
             okxSocketClient.UnifiedApi.ExchangeData.SubscribeToTickerUpdatesAsync("ETH-BTC", data => UpdateData("OKX", data.Data.LastPrice ?? 0)),
             // Toobit doesn't support the ETH/BTC pair
             //toobitSocketClient.SpotApi.SubscribeToTickerUpdatesAsync("ETHBTC", data => UpdateData("Toobit", data.Data.LastPrice ?? 0)),

Examples/BlazorClient/Pages/OrderBooks.razor

@@ -7,6 +7,7 @@
 @using Bitget.Net.Interfaces;
 @using BitMart.Net.Interfaces;
 @using BitMEX.Net.Interfaces;
+@using BloFin.Net.Interfaces;
 @using Bybit.Net.Interfaces
 @using CoinEx.Net.Interfaces
 @using CoinW.Net.Interfaces
@@ -32,6 +33,7 @@
 @inject IBitgetOrderBookFactory bitgetFactory
 @inject IBitMartOrderBookFactory bitmartFactory
 @inject IBitMEXOrderBookFactory bitmexFactory
+@inject IBloFinOrderBookFactory bloFinFactory
 @inject IBybitOrderBookFactory bybitFactory
 @inject ICoinbaseOrderBookFactory coinbaseFactory
 @inject ICoinExOrderBookFactory coinExFactory
@@ -55,7 +57,7 @@
     @foreach(var book in _books.OrderBy(p => p.Key))
     {
         <div style="margin-bottom: 20px; flex: 1; min-width: 300px;">
-            <h4>@book.Key</h4>
+            <h4>@book.Key - @book.Value.Symbol</h4>
             @if (book.Value.AskCount >= 3 && book.Value.BidCount >= 3)
             {
                 for (var i = 0; i < 3; i++)
@@ -87,23 +89,21 @@
                 { "Bitget", bitgetFactory.CreateSpot("ETHBTC") },
                 { "BitMart", bitmartFactory.CreateSpot("ETH_BTC", null) },
                 { "BitMEX", bitmexFactory.Create("ETH_XBT") },
+                { "BloFin", bloFinFactory.CreateFutures("ETH-USDT") },
                 { "Bybit", bybitFactory.Create("ETHBTC", Bybit.Net.Enums.Category.Spot) },
                 { "Coinbase", coinbaseFactory.Create("ETH-BTC", null) },
                 { "CoinEx", coinExFactory.CreateSpot("ETHBTC") },
                 { "CoinW", coinWFactory.CreateSpot("ETH_BTC") },
                 { "CryptoCom", cryptocomFactory.Create("ETH_BTC") },
                 { "GateIo", gateioFactory.CreateSpot("ETH_BTC") },
-                // DeepCoin does not support the ETH/BTC pair
-                //{ "DeepCoin", deepCoinFactory.Create("ETH-BTC") },
+                { "DeepCoin", deepCoinFactory.Create("ETH-USDT") },
                 { "HTX", htxFactory.CreateSpot("ethbtc") },
-                // HyperLiquid does not support the ETH/BTC pair
-                //{ "HyperLiquid", hyperLiquidFactory.Create("ETH/BTC") },
+                { "HyperLiquid", hyperLiquidFactory.Create("UETH/USDC") },
                 { "Kraken", krakenFactory.CreateSpot("ETH/BTC") },
                 { "Kucoin", kucoinFactory.CreateSpot("ETH-BTC") },
                 { "Mexc", mexcFactory.CreateSpot("ETHBTC") },
                 { "OKX", okxFactory.Create("ETH-BTC") },
-                // Toobit does not support the ETH/BTC pair
-                //{ "Toobit", toobitFactory.Create("ETH/BTC") },
+                { "Toobit", toobitFactory.CreateSpot("ETHUSDT") },
                 { "WhiteBit", whitebitFactory.CreateV4("ETH_BTC") },
                 { "XT", xtFactory.CreateSpot("eth_btc") },
             };

Examples/BlazorClient/Pages/Trackers.razor

@@ -7,6 +7,7 @@
 @using Bitget.Net.Interfaces;
 @using BitMEX.Net.Interfaces;
 @using BitMart.Net.Interfaces;
+@using BloFin.Net.Interfaces
 @using Bybit.Net.Interfaces
 @using CoinEx.Net.Interfaces
 @using CoinW.Net.Interfaces
@@ -33,6 +34,7 @@
 @inject IBitgetTrackerFactory bitgetFactory
 @inject IBitMartTrackerFactory bitmartFactory
 @inject IBitMEXTrackerFactory bitmexFactory
+@inject IBloFinTrackerFactory bloFinFactory
 @inject IBybitTrackerFactory bybitFactory
 @inject ICoinbaseTrackerFactory coinbaseFactory
 @inject ICoinExTrackerFactory coinExFactory
@@ -71,33 +73,35 @@
 
     protected override async Task OnInitializedAsync()
     {
-        var usdtSymbol = new SharedSymbol(TradingMode.Spot, "BTC", "USDT");
+        var usdcSpotSymbol = new SharedSymbol(TradingMode.Spot, "BTC", "USDC");
+        var usdtSpotSymbol = new SharedSymbol(TradingMode.Spot, "BTC", "USDT");
+        var usdtPerpLinSymbol = new SharedSymbol(TradingMode.PerpetualLinear, "BTC", "USDT");
 
         _trackers = new List<ITradeTracker>
             {
-                { binanceFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { bingXFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { bitfinexFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { bitgetFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { bitmartFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { bitmexFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { bybitFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { coinbaseFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { coinExFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { coinWFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { cryptocomFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { deepCoinFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { gateioFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { htxFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                // HyperLiquid doesn't support spot pair, but does have a futures BTC/USDC pair
-                { hyperLiquidFactory.CreateTradeTracker(new SharedSymbol(TradingMode.PerpetualLinear, "BTC", "USDC"), period: TimeSpan.FromMinutes(5)) },
-                { krakenFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { kucoinFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { mexcFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { okxFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { toobitFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { whitebitFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
-                { xtFactory.CreateTradeTracker(usdtSymbol, period: TimeSpan.FromMinutes(5)) },
+                { binanceFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { bingXFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { bitfinexFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { bitgetFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { bitmartFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { bitmexFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { bloFinFactory.CreateTradeTracker(usdtPerpLinSymbol, period: TimeSpan.FromMinutes(5)) },
+                { bybitFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { coinbaseFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { coinExFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { coinWFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { cryptocomFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { deepCoinFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { gateioFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { htxFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { hyperLiquidFactory.CreateTradeTracker(usdcSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { krakenFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { kucoinFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { mexcFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { okxFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { toobitFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { whitebitFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
+                { xtFactory.CreateTradeTracker(usdtSpotSymbol, period: TimeSpan.FromMinutes(5)) },
             };
 
         await Task.WhenAll(_trackers.Select(b => b.StartAsync()));

Examples/BlazorClient/Startup.cs

@@ -38,6 +38,7 @@ namespace BlazorClient
             services.AddBitget();
             services.AddBitMart();
             services.AddBitMEX();
+            services.AddBloFin();
             services.AddBybit();
             services.AddCoinbase();
             services.AddCoinEx();

Examples/BlazorClient/_Imports.razor

@@ -14,6 +14,7 @@
 @using Bitget.Net.Interfaces.Clients;
 @using BitMart.Net.Interfaces.Clients;
 @using BitMEX.Net.Interfaces.Clients;
+@using BloFin.Net.Interfaces.Clients;
 @using Bybit.Net.Interfaces.Clients;
 @using Coinbase.Net.Interfaces.Clients;
 @using CoinEx.Net.Interfaces.Clients;

README.md

@@ -18,6 +18,7 @@ Full list of all libraries part of the CryptoExchange.Net ecosystem. Consider us
 |![Bitget](https://raw.githubusercontent.com/JKorf/Bitget.Net/refs/heads/main/Bitget.Net/Icon/icon.png)|Bitget|CEX|[JKorf/Bitget.Net](https://github.com/JKorf/Bitget.Net)|[![Nuget version](https://img.shields.io/nuget/v/JK.Bitget.net.svg?style=flat-square)](https://www.nuget.org/packages/JK.Bitget.Net)|[Link](https://partner.bitget.com/bg/1qlf6pj1)|20%|
 |![BitMart](https://raw.githubusercontent.com/JKorf/BitMart.Net/refs/heads/main/BitMart.Net/Icon/icon.png)|BitMart|CEX|[JKorf/BitMart.Net](https://github.com/JKorf/BitMart.Net)|[![Nuget version](https://img.shields.io/nuget/v/BitMart.net.svg?style=flat-square)](https://www.nuget.org/packages/BitMart.Net)|[Link](https://www.bitmart.com/invite/JKorfAPI/en-US)|30%|
 |![BitMEX](https://raw.githubusercontent.com/JKorf/BitMEX.Net/refs/heads/main/BitMEX.Net/Icon/icon.png)|BitMEX|CEX|[JKorf/BitMEX.Net](https://github.com/JKorf/BitMEX.Net)|[![Nuget version](https://img.shields.io/nuget/v/JKorf.BitMEX.net.svg?style=flat-square)](https://www.nuget.org/packages/JKorf.BitMEX.Net)|[Link](https://www.bitmex.com/app/register/94f98e)|30%|
+|![BloFin](https://raw.githubusercontent.com/JKorf/BloFin.Net/refs/heads/main/BloFin.Net/Icon/icon.png)|BloFin|CEX|[JKorf/BloFin.Net](https://github.com/JKorf/BloFin.Net)|[![Nuget version](https://img.shields.io/nuget/v/BloFin.net.svg?style=flat-square)](https://www.nuget.org/packages/BloFin.Net)|-|-|
 |![Bybit](https://raw.githubusercontent.com/JKorf/Bybit.Net/refs/heads/main/ByBit.Net/Icon/icon.png)|Bybit|CEX|[JKorf/Bybit.Net](https://github.com/JKorf/Bybit.Net)|[![Nuget version](https://img.shields.io/nuget/v/Bybit.net.svg?style=flat-square)](https://www.nuget.org/packages/Bybit.Net)|[Link](https://partner.bybit.com/b/jkorf)|-|
 |![Coinbase](https://raw.githubusercontent.com/JKorf/Coinbase.Net/refs/heads/main/Coinbase.Net/Icon/icon.png)|Coinbase|CEX|[JKorf/Coinbase.Net](https://github.com/JKorf/Coinbase.Net)|[![Nuget version](https://img.shields.io/nuget/v/JKorf.Coinbase.Net.svg?style=flat-square)](https://www.nuget.org/packages/JKorf.Coinbase.Net)|[Link](https://advanced.coinbase.com/join/T6H54H8)|-|
 |![CoinEx](https://raw.githubusercontent.com/JKorf/CoinEx.Net/refs/heads/master/CoinEx.Net/Icon/icon.png)|CoinEx|CEX|[JKorf/CoinEx.Net](https://github.com/JKorf/CoinEx.Net)|[![Nuget version](https://img.shields.io/nuget/v/CoinEx.net.svg?style=flat-square)](https://www.nuget.org/packages/CoinEx.Net)|[Link](https://www.coinex.com/register?rc=rbtnp)|20%|
@@ -38,6 +39,10 @@ Full list of all libraries part of the CryptoExchange.Net ecosystem. Consider us
 
 Any of these can be installed independently or install [CryptoClients.Net](https://github.com/jkorf/CryptoClients.Net) which includes all exchange API's.
 
+### Full demo application
+A full demo application is available using the [CryptoClients.Net](https://github.com/jkorf/CryptoClients.Net) library:  
+https://github.com/JKorf/CryptoManager.Net
+
 ## Discord
 [![Nuget version](https://img.shields.io/discord/847020490588422145?style=for-the-badge)](https://discord.gg/MSpeEtSY8t)  
 A Discord server is available [here](https://discord.gg/MSpeEtSY8t). Feel free to join for discussion and/or questions around the CryptoExchange.Net and implementation libraries.
@@ -59,6 +64,14 @@ Make a one time donation in a crypto currency of your choice. If you prefer to d
 Alternatively, sponsor me on Github using [Github Sponsors](https://github.com/sponsors/JKorf). 
 
 ## Release notes
+* Version 9.8.0 - 30 Sep 2025
+    * Added ContractAddress to SharedAsset model
+    * Added ITrackerFactory interface
+    * Fixed UpdateSubscription still propagating connection events even though the specific listener is unsubscribed
+    * Fixed ExchangeHelpers.AdjustValueStep high precision calculation
+    * Fixed issue increasing the number of websocket connections increasing when sending a query when a previous connection was attempting to reconnect
+    * Fixed EnumConverter to allow mapping empty string values
+
 * Version 9.7.0 - 01 Sep 2025
     * Added LibraryHelpers.CreateHttpClientMessageHandle to standardize HttpMessageHandler creation
     * Added REST client option for selecting HTTP protocol version