diff --git a/demos/gnuradio/hackrf_file_tx_demo.grc b/demos/gnuradio/hackrf_file_tx_demo.grc
index 59d7f38..37c7721 100644
--- a/demos/gnuradio/hackrf_file_tx_demo.grc
+++ b/demos/gnuradio/hackrf_file_tx_demo.grc
@@ -49,7 +49,7 @@ blocks:
   id: variable
   parameters:
     comment: ''
-    value: '929937500'
+    value: '931937500'
   states:
     bus_sink: false
     bus_source: false
@@ -242,44 +242,285 @@ blocks:
     coordinate: [200, 12.0]
     rotation: 0
     state: true
-- name: rational_resampler_xxx_0
-  id: rational_resampler_xxx
+- name: osmosdr_sink_0
+  id: osmosdr_sink
   parameters:
     affinity: ''
     alias: ''
+    ant0: '1'
+    ant1: ''
+    ant10: ''
+    ant11: ''
+    ant12: ''
+    ant13: ''
+    ant14: ''
+    ant15: ''
+    ant16: ''
+    ant17: ''
+    ant18: ''
+    ant19: ''
+    ant2: ''
+    ant20: ''
+    ant21: ''
+    ant22: ''
+    ant23: ''
+    ant24: ''
+    ant25: ''
+    ant26: ''
+    ant27: ''
+    ant28: ''
+    ant29: ''
+    ant3: ''
+    ant30: ''
+    ant31: ''
+    ant4: ''
+    ant5: ''
+    ant6: ''
+    ant7: ''
+    ant8: ''
+    ant9: ''
+    args: hackrf=0
+    bb_gain0: '20'
+    bb_gain1: '20'
+    bb_gain10: '20'
+    bb_gain11: '20'
+    bb_gain12: '20'
+    bb_gain13: '20'
+    bb_gain14: '20'
+    bb_gain15: '20'
+    bb_gain16: '20'
+    bb_gain17: '20'
+    bb_gain18: '20'
+    bb_gain19: '20'
+    bb_gain2: '20'
+    bb_gain20: '20'
+    bb_gain21: '20'
+    bb_gain22: '20'
+    bb_gain23: '20'
+    bb_gain24: '20'
+    bb_gain25: '20'
+    bb_gain26: '20'
+    bb_gain27: '20'
+    bb_gain28: '20'
+    bb_gain29: '20'
+    bb_gain3: '20'
+    bb_gain30: '20'
+    bb_gain31: '20'
+    bb_gain4: '20'
+    bb_gain5: '20'
+    bb_gain6: '20'
+    bb_gain7: '20'
+    bb_gain8: '20'
+    bb_gain9: '20'
+    bw0: '0'
+    bw1: '0'
+    bw10: '0'
+    bw11: '0'
+    bw12: '0'
+    bw13: '0'
+    bw14: '0'
+    bw15: '0'
+    bw16: '0'
+    bw17: '0'
+    bw18: '0'
+    bw19: '0'
+    bw2: '0'
+    bw20: '0'
+    bw21: '0'
+    bw22: '0'
+    bw23: '0'
+    bw24: '0'
+    bw25: '0'
+    bw26: '0'
+    bw27: '0'
+    bw28: '0'
+    bw29: '0'
+    bw3: '0'
+    bw30: '0'
+    bw31: '0'
+    bw4: '0'
+    bw5: '0'
+    bw6: '0'
+    bw7: '0'
+    bw8: '0'
+    bw9: '0'
+    clock_source0: ''
+    clock_source1: ''
+    clock_source2: ''
+    clock_source3: ''
+    clock_source4: ''
+    clock_source5: ''
+    clock_source6: ''
+    clock_source7: ''
     comment: ''
-    decim: int(samp_rate // math.gcd(int(hw_rate), int(samp_rate)))
-    fbw: '0'
-    interp: int(hw_rate // math.gcd(int(hw_rate), int(samp_rate)))
+    corr0: '0.8'
+    corr1: '0'
+    corr10: '0'
+    corr11: '0'
+    corr12: '0'
+    corr13: '0'
+    corr14: '0'
+    corr15: '0'
+    corr16: '0'
+    corr17: '0'
+    corr18: '0'
+    corr19: '0'
+    corr2: '0'
+    corr20: '0'
+    corr21: '0'
+    corr22: '0'
+    corr23: '0'
+    corr24: '0'
+    corr25: '0'
+    corr26: '0'
+    corr27: '0'
+    corr28: '0'
+    corr29: '0'
+    corr3: '0'
+    corr30: '0'
+    corr31: '0'
+    corr4: '0'
+    corr5: '0'
+    corr6: '0'
+    corr7: '0'
+    corr8: '0'
+    corr9: '0'
+    freq0: center_freq
+    freq1: 100e6
+    freq10: 100e6
+    freq11: 100e6
+    freq12: 100e6
+    freq13: 100e6
+    freq14: 100e6
+    freq15: 100e6
+    freq16: 100e6
+    freq17: 100e6
+    freq18: 100e6
+    freq19: 100e6
+    freq2: 100e6
+    freq20: 100e6
+    freq21: 100e6
+    freq22: 100e6
+    freq23: 100e6
+    freq24: 100e6
+    freq25: 100e6
+    freq26: 100e6
+    freq27: 100e6
+    freq28: 100e6
+    freq29: 100e6
+    freq3: 100e6
+    freq30: 100e6
+    freq31: 100e6
+    freq4: 100e6
+    freq5: 100e6
+    freq6: 100e6
+    freq7: 100e6
+    freq8: 100e6
+    freq9: 100e6
+    gain0: '40'
+    gain1: '10'
+    gain10: '10'
+    gain11: '10'
+    gain12: '10'
+    gain13: '10'
+    gain14: '10'
+    gain15: '10'
+    gain16: '10'
+    gain17: '10'
+    gain18: '10'
+    gain19: '10'
+    gain2: '10'
+    gain20: '10'
+    gain21: '10'
+    gain22: '10'
+    gain23: '10'
+    gain24: '10'
+    gain25: '10'
+    gain26: '10'
+    gain27: '10'
+    gain28: '10'
+    gain29: '10'
+    gain3: '10'
+    gain30: '10'
+    gain31: '10'
+    gain4: '10'
+    gain5: '10'
+    gain6: '10'
+    gain7: '10'
+    gain8: '10'
+    gain9: '10'
+    if_gain0: '20'
+    if_gain1: '20'
+    if_gain10: '20'
+    if_gain11: '20'
+    if_gain12: '20'
+    if_gain13: '20'
+    if_gain14: '20'
+    if_gain15: '20'
+    if_gain16: '20'
+    if_gain17: '20'
+    if_gain18: '20'
+    if_gain19: '20'
+    if_gain2: '20'
+    if_gain20: '20'
+    if_gain21: '20'
+    if_gain22: '20'
+    if_gain23: '20'
+    if_gain24: '20'
+    if_gain25: '20'
+    if_gain26: '20'
+    if_gain27: '20'
+    if_gain28: '20'
+    if_gain29: '20'
+    if_gain3: '20'
+    if_gain30: '20'
+    if_gain31: '20'
+    if_gain4: '20'
+    if_gain5: '20'
+    if_gain6: '20'
+    if_gain7: '20'
+    if_gain8: '20'
+    if_gain9: '20'
     maxoutbuf: '0'
     minoutbuf: '0'
-    taps: '[]'
-    type: ccc
+    nchan: '1'
+    num_mboards: '1'
+    sample_rate: hw_rate
+    sync: sync
+    time_source0: ''
+    time_source1: ''
+    time_source2: ''
+    time_source3: ''
+    time_source4: ''
+    time_source5: ''
+    time_source6: ''
+    time_source7: ''
+    type: fc32
   states:
     bus_sink: false
     bus_source: false
     bus_structure: null
-    coordinate: [1152, 252.0]
+    coordinate: [928, 460.0]
     rotation: 0
-    state: enabled
-- name: soapy_hackrf_sink_0
-  id: soapy_hackrf_sink
+    state: true
+- name: rational_resampler_xxx_0
+  id: rational_resampler_xxx
   parameters:
     affinity: ''
     alias: ''
-    amp: 'False'
-    bandwidth: '0'
-    center_freq: center_freq
     comment: ''
-    dev_args: ''
-    samp_rate: hw_rate
-    type: fc32
-    vga: '28'
+    decim: int(samp_rate // math.gcd(int(hw_rate), int(samp_rate)))
+    fbw: '0'
+    interp: int(hw_rate // math.gcd(int(hw_rate), int(samp_rate)))
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    taps: '[]'
+    type: ccc
   states:
     bus_sink: false
     bus_source: false
     bus_structure: null
-    coordinate: [1152, 368.0]
+    coordinate: [1152, 252.0]
     rotation: 0
     state: enabled
 
@@ -291,7 +532,7 @@ connections:
 - [blocks_throttle_0, '0', rational_resampler_xxx_0, '0']
 - [blocks_uchar_to_float_0, '0', blocks_add_const_vxx_0, '0']
 - [blocks_unpack_k_bits_bb_0, '0', blocks_repeat_0, '0']
-- [rational_resampler_xxx_0, '0', soapy_hackrf_sink_0, '0']
+- [rational_resampler_xxx_0, '0', osmosdr_sink_0, '0']
 
 metadata:
   file_format: 1
diff --git a/demos/hackrf_tcp_server/Makefile b/demos/hackrf_tcp_server/Makefile
index 049213d..6da12f4 100644
--- a/demos/hackrf_tcp_server/Makefile
+++ b/demos/hackrf_tcp_server/Makefile
@@ -7,7 +7,7 @@ SRC = main.cpp
 
 all: $(TARGET)
 
-$(TARGET): $(SRC) json.hpp
+$(TARGET): $(SRC)
 	$(CXX) $(CXXFLAGS) -o $(TARGET) $(SRC) $(LDFLAGS)
 
 clean:
diff --git a/demos/hackrf_tcp_server/include/config.hpp b/demos/hackrf_tcp_server/include/config.hpp
index 9221e67..c05c682 100644
--- a/demos/hackrf_tcp_server/include/config.hpp
+++ b/demos/hackrf_tcp_server/include/config.hpp
@@ -36,63 +36,57 @@ inline bool load_config(const std::string& filename, Config& cfg) {
         val.erase(0, val.find_first_not_of(" \t"));
         val.erase(val.find_last_not_of(" \t") + 1);
 
-        switch (key) {
-            case "PORT":
-                try {
-                    cfg.PORT = std::stoul(val);
-                } catch (...) {
-                    std::cerr << "Invalid PORT value: " << val << std::endl;
-                    return false;
-                }
-                break;
-
-            case "SAMPLE_RATE":
-                try {
-                    cfg.SAMPLE_RATE = std::stoull(val);
-                } catch (...) {
-                    std::cerr << "Invalid SAMPLE_RATE value: " << val << std::endl;
-                    return false;
-                }
-                break;
-
-            case "BITRATE":
-                try {
-                    cfg.BITRATE = std::stoul(val);
-                } catch (...) {
-                    std::cerr << "Invalid BITRATE value: " << val << std::endl;
-                    return false;
-                }
-                break;
-
-            case "AMPLITUDE":
-                try {
-                    cfg.AMPLITUDE = static_cast<int8_t>(std::stoi(val));
-                } catch (...) {
-                    std::cerr << "Invalid AMPLITUDE value: " << val << std::endl;
-                    return false;
-                }
-                break;
-
-            case "FREQ_DEV":
-                try {
-                    cfg.FREQ_DEV = std::stoul(val);
-                } catch (...) {
-                    std::cerr << "Invalid FREQ_DEV value: " << val << std::endl;
-                    return false;
-                }
-                break;
-            case "TX_GAIN":
-                try {
-                    cfg.TX_GAIN = static_cast<uint8_t>(std::stoi(val));
-                } catch (...) {
-                    std::cerr << "Invalid TX_GAIN value: " << val << std::endl;
-                    return false;
-                }
-                break;
-
-            default:
-                std::cerr << "Unknown configuration key: " << key << std::endl;
+        if (key == "PORT") {
+            try {
+                cfg.PORT = std::stoul(val);
+            } catch (...) {
+                std::cerr << "Invalid PORT value: " << val << std::endl;
+                return false;
+            }
+        }
+        else if (key == "SAMPLE_RATE") {
+            try {
+                cfg.SAMPLE_RATE = std::stoull(val);
+            } catch (...) {
+                std::cerr << "Invalid SAMPLE_RATE value: " << val << std::endl;
+                return false;
+            }
+        }
+        else if (key == "BITRATE") {
+            try {
+                cfg.BITRATE = std::stoul(val);
+            } catch (...) {
+                std::cerr << "Invalid BITRATE value: " << val << std::endl;
+                return false;
+            }
+        }
+        else if (key == "AMPLITUDE") {
+            try {
+                cfg.AMPLITUDE = static_cast<int8_t>(std::stoi(val));
+            } catch (...) {
+                std::cerr << "Invalid AMPLITUDE value: " << val << std::endl;
+                return false;
+            }
+        }
+        else if (key == "FREQ_DEV") {
+            try {
+                cfg.FREQ_DEV = std::stoul(val);
+            } catch (...) {
+                std::cerr << "Invalid FREQ_DEV value: " << val << std::endl;
+                return false;
+            }
+        }
+        else if (key == "TX_GAIN") {
+            try {
+                cfg.TX_GAIN = static_cast<uint8_t>(std::stoi(val));
+            } catch (...) {
+                std::cerr << "Invalid TX_GAIN value: " << val << std::endl;
                 return false;
+            }
+        }
+        else {
+            std::cerr << "Unknown configuration key: " << key << std::endl;
+            return false;
         }
     }
 
diff --git a/demos/hackrf_tcp_server/include/flex_util.hpp b/demos/hackrf_tcp_server/include/flex_util.hpp
index 5e198df..643efe9 100644
--- a/demos/hackrf_tcp_server/include/flex_util.hpp
+++ b/demos/hackrf_tcp_server/include/flex_util.hpp
@@ -5,7 +5,7 @@
 #include <string>
 #include "../../../tinyflex.h"
 
-inline bool encode_flex_message(const std::string& message, int capcode, uint8_t* flex_buffer, size_t flex_buffer_size, size_t& flex_len, int& error) {
+inline bool encode_flex_message(const std::string& message, uint64_t capcode, uint8_t* flex_buffer, size_t flex_buffer_size, size_t& flex_len, int& error) {
     memset(flex_buffer, 0, flex_buffer_size);
     error = 0;
     flex_len = tf_encode_flex_message(message.c_str(), capcode, flex_buffer, flex_buffer_size, &error);
diff --git a/demos/hackrf_tcp_server/main.cpp b/demos/hackrf_tcp_server/main.cpp
index 494b9e0..c5cafc8 100644
--- a/demos/hackrf_tcp_server/main.cpp
+++ b/demos/hackrf_tcp_server/main.cpp
@@ -84,14 +84,18 @@ int main(int argc, char* argv[]) {
         std::string message     = input.substr(pos1 + 1, pos2 - pos1 - 1);
         std::string freq_str    = input.substr(pos2 + 1);
 
+        uint64_t capcode;
+        long frequency;
+
         try {
-            uint64_t capcode = std::stoull(capcode_str);
-            if (tinyflex::is_capcode_valid(capcode) == 0) {
+            capcode = std::stoull(capcode_str);
+            int is_long;
+            if (!is_capcode_valid(capcode, &is_long)) {
                 throw std::invalid_argument("Invalid capcode: " + capcode_str);
             }
         } catch (const std::invalid_argument& e) {
-            std::string error_msg = std::to_string(error);
-            printf("%s\n", error_msg);
+            std::string error_msg = "Invalid capcode: " + capcode_str;
+            printf("%s\n", error_msg.c_str());
 
             // Send message back to client
             send(client_fd, error_msg.c_str(), error_msg.size(), 0);
@@ -100,7 +104,7 @@ int main(int argc, char* argv[]) {
             continue;
         } catch (const std::out_of_range& e) {
             std::string error_msg = "Capcode out of range: " + capcode_str;
-            printf("%s\n", error_msg);
+            printf("%s\n", error_msg.c_str());
 
             // Send message back to client
             send(client_fd, error_msg.c_str(), error_msg.size(), 0);
@@ -110,20 +114,20 @@ int main(int argc, char* argv[]) {
         }
 
         try {
-            long frequency = std::stoul(freq_str);
+            frequency = std::stoul(freq_str);
             if (frequency < 1000000 || frequency > 6000000000) {
                 throw std::out_of_range("Frequency out of valid range: " + freq_str);
             }
         } catch (const std::invalid_argument& e) {
-            std::string error_msg = "Invalid frequency: " + std::to_string(error);
-            printf("%s\n", error_msg);
+            std::string error_msg = "Invalid frequency: " + freq_str;
+            printf("%s\n", error_msg.c_str());
             // Send message back to client
             send(client_fd, error_msg.c_str(), error_msg.size(), 0);
             close(client_fd);
             continue;
         } catch (const std::out_of_range& e) {
-            std::string error_msg = std::to_string(error);
-            printf("%s\n", error_msg);
+            std::string error_msg = "Frequency out of valid range: " + freq_str;
+            printf("%s\n", error_msg.c_str());
 
             // Send message back to client
             send(client_fd, error_msg.c_str(), error_msg.size(), 0);
@@ -131,7 +135,8 @@ int main(int argc, char* argv[]) {
             continue;
         }
 
-        printf("Received: CAPCODE=%d, MESSAGE='%s', FREQUENCY=%d\n", capcode, message.c_str(), frequency);
+        printf("Received: CAPCODE=%llu, MESSAGE='%s', FREQUENCY=%ld\n",
+               (unsigned long long)capcode, message.c_str(), frequency);
 
         // Encode message using TinyFlex
         uint8_t flex_buffer[1024];
@@ -154,7 +159,7 @@ int main(int argc, char* argv[]) {
             for (size_t i = 0; i < flex_len; ++i) {
                 printf("%02X ", flex_buffer[i]);
             }
-            
+
             printf("\n");
         }
 
@@ -165,8 +170,6 @@ int main(int argc, char* argv[]) {
             continue;
         }
 
-        int result = 0;
-
         // Generate FSK IQ samples from FLEX buffer
         std::vector<int8_t> iq_samples = generate_fsk_iq_samples(
             flex_buffer,
@@ -200,4 +203,4 @@ int main(int argc, char* argv[]) {
 
     close(server_fd);
     return 0;
-}
\ No newline at end of file
+}