diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7cbe745..e51ea82 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -14,15 +14,19 @@ SET(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 SET(SOURCES 
   src/lib.cpp)
 
-ADD_EXECUTABLE(test_async tests/test_lib.cpp ${SOURCES})
+ADD_EXECUTABLE(test_async tests/test_async.cpp ${SOURCES})
 TARGET_LINK_LIBRARIES(test_async)
 
 ADD_EXECUTABLE(test_lib tests/test_lib.cpp ${SOURCES})
 TARGET_LINK_LIBRARIES(test_lib)
 
+ADD_EXECUTABLE(test_parser tests/test_parser.cpp ${SOURCES})
+TARGET_LINK_LIBRARIES(test_parser)
+
 ADD_EXECUTABLE(run_app src/main.cpp ${SOURCES})
 TARGET_LINK_LIBRARIES(run_app)
 
 ENABLE_TESTING()
 ADD_TEST(AsyncTests bin/test_async)
-ADD_TEST(LibTests bin/test_lib)
\ No newline at end of file
+ADD_TEST(LibTests bin/test_lib)
+ADD_TEST(ParserTests bin/test_parser)
\ No newline at end of file
diff --git a/include/exchange/concepts.hpp b/include/exchange/concepts.hpp
new file mode 100644
index 0000000..443fa02
--- /dev/null
+++ b/include/exchange/concepts.hpp
@@ -0,0 +1,51 @@
+#ifndef INCLUDED_EXCHANGE_CONCEPTS_HPP
+#define INCLUDED_EXCHANGE_CONCEPTS_HPP
+
+#include "util/concepts.hpp"
+
+
+namespace sadhbhcraft::exchange {
+
+    template <typename T>
+    concept MsgParserConcept =
+        requires(T &x) {
+            util::NumberConcept<typename T::KeyType>;
+            util::NumberConcept<typename T::IntegerType>;
+            util::NumberConcept<typename T::DecimalType>;
+            typename T::StringType;
+            {
+                x.parse_key(
+                    std::declval<typename T::KeyType &>())
+                } -> std::convertible_to<bool>;
+            {
+                x.parse_value(
+                    std::declval<typename T::IntegerType &>())
+                } -> std::convertible_to<bool>;
+            {
+                x.parse_value(
+                    std::declval<typename T::DecimalType &>())
+                } -> std::convertible_to<bool>;
+            {
+                x.parse_value(
+                    std::declval<typename T::StringType &>())
+                } -> std::convertible_to<bool>;
+            {
+                x.parse_field(
+                    std::declval<typename T::KeyType>(),
+                    std::declval<typename T::IntegerType &>())
+                } -> std::convertible_to<bool>;
+            {
+                x.parse_field(
+                    std::declval<typename T::KeyType>(),
+                    std::declval<typename T::DecimalType &>())
+                } -> std::convertible_to<bool>;
+            {
+                x.parse_field(
+                    std::declval<typename T::KeyType>(),
+                    std::declval<typename T::StringType &>())
+                } -> std::convertible_to<bool>;
+        };
+
+
+} // end of namespace sadhbhcraft::exchange
+#endif//INCLUDED_EXCHANGE_CONCEPTS_HPP
\ No newline at end of file
diff --git a/include/exchange/istream_msg_parser.hpp b/include/exchange/istream_msg_parser.hpp
new file mode 100644
index 0000000..3c8ca23
--- /dev/null
+++ b/include/exchange/istream_msg_parser.hpp
@@ -0,0 +1,93 @@
+#ifndef INCLUDED_SIMPLE_PARSER_HPP
+#define INCLUDED_SIMPLE_PARSER_HPP
+
+#include "util/concepts.hpp"
+
+#include <istream>
+
+
+namespace sadhbhcraft::exchange {
+
+    template<util::NumberConcept _KeyType>
+    class IStreamMsgParser
+    {
+    public:
+        using KeyType = _KeyType;
+        using StringType = std::string;
+        using IntegerType = int;
+        using DecimalType = double;
+
+        IStreamMsgParser(std::istream &is): m_is(is) {}
+    
+        bool parse_key(KeyType &out_key)
+        {
+            if (m_is.eof())
+            {
+                return false;
+            }
+
+            m_is >> out_key;
+            
+            if (auto c = m_is.get(); c != '=')
+            {
+                return false;
+            }
+
+            return true;
+        }
+        
+        bool parse_value(util::NumberConcept auto &out_value)
+        {
+            if (m_is.eof())
+            {
+                return false;
+            }
+
+            m_is >> out_value;
+            
+            if (auto c = m_is.get(); c != '\1' && !m_is.eof())
+            {
+                return false;
+            }
+
+            return true;
+        }
+        
+        bool parse_value(std::string &out_value)
+        {
+            if (m_is.eof())
+            {
+                return false;
+            }
+
+            for (;;)
+            {
+                auto c = m_is.get();
+
+                if (c == '\1' || m_is.eof())
+                {
+                    break;
+                }
+                out_value += c;
+            }
+
+            return true;
+        }
+
+        bool parse_field(KeyType in_key, auto &out_value)
+        {
+            if (KeyType key; parse_key(key), key != in_key)
+            { 
+                return false;
+            }
+
+            return parse_value(out_value);
+        }
+
+    private:
+        std::istream &m_is;
+    };
+
+
+} // end of namespace sadhbhcraft::exchange
+#endif//INCLUDED_SIMPLE_PARSER_HPP
\ No newline at end of file
diff --git a/include/exchange/msg_header.hpp b/include/exchange/msg_header.hpp
new file mode 100644
index 0000000..7ffe5ca
--- /dev/null
+++ b/include/exchange/msg_header.hpp
@@ -0,0 +1,43 @@
+#ifndef INCLUDED_MSG_HEADER_HPP
+#define INCLUDED_MSG_HEADER_HPP
+
+#include "exchange/concepts.hpp"
+
+
+namespace sadhbhcraft::exchange {
+
+    template <MsgParserConcept MsgParserType>
+    struct MsgHeader
+    {
+        using KeyType = typename MsgParserType::KeyType;
+        using StringType = typename MsgParserType::StringType;
+        using IntegerType = typename MsgParserType::IntegerType;
+        
+        static constexpr KeyType FixVersion = 8;
+        static constexpr KeyType BodyLength = 9;
+        static constexpr KeyType MsgType = 35;
+        static constexpr KeyType SenderCompId = 49;
+        static constexpr KeyType TargetCompId = 56;
+        static constexpr KeyType ApplVerID = 1128;
+        static constexpr KeyType Checksum = 10;
+        
+        StringType fix_version;
+        StringType sender_comp_id;
+        StringType target_comp_id;
+        IntegerType body_length;
+        IntegerType msg_type;
+
+        template<typename P>
+        bool parse_message(P &&parser) requires std::is_same_v<std::remove_cvref_t<P>, MsgParserType>
+        {
+            // These fields must be in this exact order
+            return parser.parse_field(FixVersion, fix_version) &&
+                   parser.parse_field(BodyLength, body_length) &&
+                   parser.parse_field(MsgType, msg_type) &&
+                   parser.parse_field(SenderCompId, sender_comp_id) &&
+                   parser.parse_field(TargetCompId, target_comp_id);
+        }
+    };
+
+} // end of namespace sadhbhcraft::exchange
+#endif//INCLUDED_MSG_HEADER_HPP
\ No newline at end of file
diff --git a/include/exchange/msg_new_order_single.hpp b/include/exchange/msg_new_order_single.hpp
new file mode 100644
index 0000000..72e1178
--- /dev/null
+++ b/include/exchange/msg_new_order_single.hpp
@@ -0,0 +1,98 @@
+#ifndef INCLUDED_MSG_NEW_ORDER_SINGLE_HPP
+#define INCLUDED_MSG_NEW_ORDER_SINGLE_HPP
+
+#include "exchange/concepts.hpp"
+
+
+namespace sadhbhcraft::exchange {
+
+    template <MsgParserConcept MsgParserType>
+    struct NewOrderSingle
+    {
+        using KeyType = typename MsgParserType::KeyType;
+        using StringType = typename MsgParserType::StringType;
+        using IntegerType = typename MsgParserType::IntegerType;
+        using DecimalType = typename MsgParserType::DecimalType;
+        
+        static constexpr KeyType ClOrdID = 11;
+        static constexpr KeyType OrdType = 40; // 1 MKT, 2 LMT
+        static constexpr KeyType Price = 44;
+        static constexpr KeyType OrderQty = 38;
+        static constexpr KeyType Side = 54; // 1 BUY, 2 SELL
+        static constexpr KeyType TransactTime = 60;
+        static constexpr KeyType Symbol = 55;
+        static constexpr KeyType TimeInForce = 59; //1 GTC, 3 IOC
+
+        unsigned
+            cl_ord_id_bit : 1 = {0},
+            transact_time_bit : 1 = {0},
+            symbol_bit : 1 = {0},
+            ord_type_bit : 1 = {0},
+            side_bit : 1 = {0},
+            time_in_force_bit : 1 = {0},
+            price_bit : 1 = {0},
+            order_qty_bit : 1 = {0};
+
+        StringType cl_ord_id;
+        StringType transact_time;
+        StringType symbol;
+        IntegerType ord_type;
+        IntegerType side;
+        IntegerType time_in_force;
+        DecimalType price;
+        DecimalType order_qty;
+
+
+        template<typename P>
+        bool parse_message(P &&parser) requires std::is_same_v<std::remove_cvref_t<P>, MsgParserType>
+        {
+            for (;;)
+            {
+                KeyType key;
+                if (!parser.parse_key(key))
+                {
+                    break;
+                }
+
+                switch (key)
+                {
+                case ClOrdID:
+                    cl_ord_id_bit = parser.parse_value(cl_ord_id);
+                    break;
+                case OrdType:
+                    ord_type_bit = parser.parse_value(ord_type);
+                    break;
+                case Price:
+                    price_bit = parser.parse_value(price);
+                    break;
+                case OrderQty:
+                    order_qty_bit = parser.parse_value(order_qty);
+                    break;
+                case Side:
+                    side_bit = parser.parse_value(side);
+                    break;
+                case TransactTime:
+                    transact_time_bit = parser.parse_value(transact_time);
+                    break;
+                case Symbol:
+                    symbol_bit = parser.parse_value(symbol);
+                    break;
+                case TimeInForce:
+                    time_in_force_bit = parser.parse_value(time_in_force);
+                    break;
+                }
+            }
+
+            return cl_ord_id_bit &&
+                   transact_time_bit &&
+                   symbol_bit &&
+                   ord_type_bit &&
+                   side_bit &&
+                   time_in_force_bit &&
+                   price_bit &&
+                   order_qty_bit;
+        }
+    };
+
+} // end of namespace sadhbhcraft::exchange
+#endif//INCLUDED_MSG_NEW_ORDER_SINGLE_HPP
\ No newline at end of file
diff --git a/include/lib.hpp b/include/lib.hpp
index 687d3a4..435d635 100644
--- a/include/lib.hpp
+++ b/include/lib.hpp
@@ -5,6 +5,5 @@
 
 namespace sadhbhcraft::orderbook
 {
-
 } // end of namespace sadhbhcraft::orderbook
 #endif // INCLUDED_LIB_HPP
\ No newline at end of file
diff --git a/src/main.cpp b/src/main.cpp
index 6f157a2..ddae438 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,6 +1,7 @@
 #include "lib.hpp"
 
 #include <iostream>
+#include <sstream>
 
 
 namespace scob = sadhbhcraft::orderbook;
diff --git a/tests/test_async.cpp b/tests/test_async.cpp
index 1113abe..0c91847 100644
--- a/tests/test_async.cpp
+++ b/tests/test_async.cpp
@@ -3,6 +3,7 @@
 #include "util/async.hpp"
 #include "util/generator.hpp"
 
+#include <functional>
 #include <vector>
 #include <iostream>
 
@@ -20,6 +21,7 @@ struct OrderQuantity
     int quantity;
 };
 
+
 class OrderSizeLimit
 {
 public:
@@ -62,7 +64,7 @@ struct Level
                     .order = iter->order, 
                     .quantity = quantity
                 };
-                co_await ep(oq);
+                co_await ep(std::ref(oq));
                 iter->quantity -= oq.quantity;
                 quantity -= oq.quantity;
                 co_yield oq;
@@ -74,7 +76,7 @@ struct Level
                     .order = iter->order, 
                     .quantity = iter->quantity
                 };
-                co_await ep(oq);
+                co_await ep(std::ref(oq));
                 quantity -= oq.quantity;
                 iter->quantity = 0; // remainder is cancelled
                 co_yield oq;
diff --git a/tests/test_parser.cpp b/tests/test_parser.cpp
new file mode 100644
index 0000000..1212b0f
--- /dev/null
+++ b/tests/test_parser.cpp
@@ -0,0 +1,132 @@
+#include "test_util.hpp"
+
+#include "exchange/istream_msg_parser.hpp"
+
+#include "exchange/msg_header.hpp"
+#include "exchange/msg_new_order_single.hpp"
+
+#include <sstream>
+#include <iostream>
+#include <cmath>
+#include <limits>
+
+
+void test_parse_msg_header()
+{
+    namespace sce = sadhbhcraft::exchange;
+
+    std::stringstream ss{"8=FIX.4.2" "\1" "9=178" "\1" "35=8" "\1" "49=PHLX" "\1" "56=PERS" };
+
+    sce::IStreamMsgParser<int> parser{ss};
+
+    sce::MsgHeader<std::remove_cvref_t<decltype(parser)>> header;
+
+    assert(header.parse_message(parser));
+
+    std::cout
+        << "FixVersion: " << header.fix_version << ", "
+        << "Sender ID: " << header.sender_comp_id << ", "
+        << "Target ID: " << header.target_comp_id << ", "
+        << "BodyLen: " << header.body_length << ", "
+        << "MsgType: " << header.msg_type
+        << std::endl;
+
+    assert(header.fix_version == "FIX.4.2");
+    assert(header.sender_comp_id == "PHLX");
+    assert(header.target_comp_id == "PERS");
+    assert(header.body_length == 178);
+    assert(header.msg_type == 8);
+}
+
+void test_parse_new_order_single()
+{
+    namespace sce = sadhbhcraft::exchange;
+
+    std::stringstream ss{
+        "11=000-001-001" "\1"
+        "40=2" "\1"
+        "44=75.250" "\1"
+        "38=50.500" "\1"
+        "54=2" "\1"
+        "60=20230412-18:10:00.000" "\1"
+        "55=BTCETH" "\1"
+        "59=1"
+    };
+
+    sce::IStreamMsgParser<int> parser{ss};
+
+    sce::NewOrderSingle<std::remove_cvref_t<decltype(parser)>> new_order;
+
+    assert(new_order.parse_message(parser));
+
+    std::cout << "ClOrdID: " << new_order.cl_ord_id
+        << ", TransactTime: " << new_order.transact_time
+        << ", Symbol: " << new_order.symbol
+        << ", OrdType: " << new_order.ord_type
+        << ", Side: " << new_order.side
+        << ", TimeInForce: " << new_order.time_in_force
+        << ", Price: " << new_order.price
+        << ", OrderQty: " << new_order.order_qty
+        << std::endl;
+
+    assert(new_order.cl_ord_id == "000-001-001");
+    assert(new_order.transact_time == "20230412-18:10:00.000");
+    assert(new_order.symbol == "BTCETH");
+    assert(new_order.ord_type == 2);
+    assert(new_order.side == 2);
+    assert(new_order.time_in_force == 1);
+    assert(std::fabs(new_order.price - 75.25) < std::numeric_limits<decltype(new_order.price)>::epsilon());
+    assert(std::fabs(new_order.order_qty - 50.5) < std::numeric_limits<decltype(new_order.order_qty)>::epsilon());
+}
+
+void test_parse_new_order_single_full_message()
+{
+    namespace sce = sadhbhcraft::exchange;
+
+    std::stringstream ss{
+        "8=FIX.4.2" "\1"
+        "9=178" "\1"
+        "35=13" "\1"
+        "49=PHLX" "\1"
+        "56=PERS" 
+        "11=000-001-001" "\1"
+        "40=2" "\1"
+        "44=75.250" "\1"
+        "38=50.500" "\1"
+        "54=2" "\1"
+        "60=20230412-18:10:00.000" "\1"
+        "55=BTCETH" "\1"
+        "59=1" "\1"
+        "10=128"
+    };
+
+    sce::IStreamMsgParser<int> parser{ss};
+
+    sce::MsgHeader<std::remove_cvref_t<decltype(parser)>> header;
+    sce::NewOrderSingle<std::remove_cvref_t<decltype(parser)>> new_order;
+
+    assert(header.parse_message(parser));
+    assert(new_order.parse_message(parser));
+    
+    assert(header.fix_version == "FIX.4.2");
+    assert(header.sender_comp_id == "PHLX");
+    assert(header.target_comp_id == "PERS");
+    assert(header.body_length == 178);
+    assert(header.msg_type == 13);
+    
+    assert(new_order.cl_ord_id == "000-001-001");
+    assert(new_order.transact_time == "20230412-18:10:00.000");
+    assert(new_order.symbol == "BTCETH");
+    assert(new_order.ord_type == 2);
+    assert(new_order.side == 2);
+    assert(new_order.time_in_force == 1);
+    assert(std::fabs(new_order.price - 75.25) < std::numeric_limits<decltype(new_order.price)>::epsilon());
+    assert(std::fabs(new_order.order_qty - 50.5) < std::numeric_limits<decltype(new_order.order_qty)>::epsilon());
+}
+
+int main(int argc, char **argv)
+{
+    test_parse_msg_header();
+    test_parse_new_order_single();
+    return 0;
+}
\ No newline at end of file