dev -> master

- Fix double framing in queue_data
- check if TCP port is available before binding
- show headers in verbose output
- Add packet fragmentation/reassembly with magic byte 0xF3
- Fragmentation enabled via --frag flag or UI toggle
- Update utility `update.sh`


Fragment header: `[MAGIC][PKT_ID:2][SEQ][FLAGS]`

README.md

@@ -98,4 +98,11 @@ while running `rigctld`
 ```
 
 
+## Updating
 
+modem73 comes included with a update utility `update.sh`
+
+To update to the latest version:
+```
+./update.sh
+```

kiss_tnc.cc

@@ -67,6 +67,27 @@ inline void ui_log(const std::string& msg) {
     }
 }
 
+bool check_port_available(const std::string& bind_address, int port) {
+    int sock = socket(AF_INET, SOCK_STREAM, 0);
+    if (sock < 0) {
+        return false;
+    }
+    
+    int opt = 1;
+    setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
+    
+    struct sockaddr_in addr;
+    memset(&addr, 0, sizeof(addr));
+    addr.sin_family = AF_INET;
+    addr.sin_addr.s_addr = inet_addr(bind_address.c_str());
+    addr.sin_port = htons(port);
+    
+    int result = bind(sock, (struct sockaddr*)&addr, sizeof(addr));
+    close(sock);
+    
+    return result == 0;
+}
+
 
 
 
@@ -208,6 +229,8 @@ public:
             std::cerr << "CSMA: disabled" << std::endl;
         }
         
+        std::cerr << "Fragmentation: " << (config_.fragmentation_enabled ? "enabled" : "disabled") << std::endl;
+        
         // Show PTT status
         switch (config_.ptt_type) {
             case PTTType::NONE:
@@ -321,47 +344,83 @@ private:
     void handle_kiss_frame(uint8_t /*port*/, uint8_t cmd, const std::vector<uint8_t>& data) {
         if (cmd == KISS::CMD_DATA) {
             if (g_verbose) {
-                hex_dump("TX Queue", data.data(), data.size());
+                std::cerr << kiss_frame_visualize(data.data(), data.size()) << std::endl;
             }
             
-            // Check size
-            if (data.size() > (size_t)payload_size_) {
-                std::cerr << "Warning: Frame too large (" << data.size() 
-                          << " > " << payload_size_ << "), truncating" << std::endl;
-            }
+            size_t max_payload = payload_size_ - 2;
             
-            tx_queue_.push(data);
+            if (config_.fragmentation_enabled && fragmenter_.needs_fragmentation(data.size(), max_payload)) {
+                auto fragments = fragmenter_.fragment(data, max_payload);
+                ui_log("TX: Fragmenting " + std::to_string(data.size()) + " bytes into " + 
+                       std::to_string(fragments.size()) + " fragments");
+                for (auto& frag : fragments) {
+                    if (g_verbose) {
+                        std::cerr << packet_visualize(frag.data(), frag.size(), true, true) << std::endl;
+                    }
+                    tx_queue_.push(std::move(frag));
+                }
 #ifdef WITH_UI
-            if (g_ui_state) {
-                g_ui_state->tx_queue_size = tx_queue_.size();
-            }
+                if (g_ui_state) {
+                    g_ui_state->tx_queue_size = tx_queue_.size();
+                }
 #endif
+            } else {
+                std::vector<uint8_t> frame_data = data;
+                if (frame_data.size() > max_payload) {
+                    std::cerr << "Warning: Frame too large (" << frame_data.size() 
+                              << " > " << max_payload << "), truncating" << std::endl;
+                    frame_data.resize(max_payload);
+                }
+                if (g_verbose) {
+                    std::cerr << packet_visualize(frame_data.data(), frame_data.size(), true, config_.fragmentation_enabled) << std::endl;
+                }
+                tx_queue_.push(frame_data);
+#ifdef WITH_UI
+                if (g_ui_state) {
+                    g_ui_state->tx_queue_size = tx_queue_.size();
+                }
+#endif
+            }
         } else {
-            // Handle KISS control commands
             switch (cmd) {
             case KISS::CMD_TXDELAY:
                 if (!data.empty()) {
                     config_.tx_delay_ms = data[0] * 10;
-                    std::cerr << "TXDelay set to " << config_.tx_delay_ms << " ms" << std::endl;
+                    ui_log("TXDelay set to " + std::to_string(config_.tx_delay_ms) + " ms");
                 }
                 break;
             case KISS::CMD_P:
                 if (!data.empty()) {
                     config_.p_persistence = data[0];
+                    ui_log("P-persistence set to " + std::to_string(config_.p_persistence));
                 }
                 break;
             case KISS::CMD_SLOTTIME:
                 if (!data.empty()) {
                     config_.slot_time_ms = data[0] * 10;
+                    ui_log("Slot time set to " + std::to_string(config_.slot_time_ms) + " ms");
+                }
+                break;
+            case KISS::CMD_TXTAIL:
+                if (!data.empty()) {
+                    config_.ptt_tail_ms = data[0] * 10;
+                    ui_log("TXTail set to " + std::to_string(config_.ptt_tail_ms) + " ms");
                 }
                 break;
             case KISS::CMD_FULLDUPLEX:
                 if (!data.empty()) {
                     config_.full_duplex = data[0] != 0;
+                    ui_log(std::string("Full duplex ") + (config_.full_duplex ? "enabled" : "disabled"));
                 }
                 break;
+            case KISS::CMD_SETHW:
+                break;
+            case KISS::CMD_RETURN:
+                break;
             default:
-                std::cerr << "Unknown KISS command: " << (int)cmd << std::endl;
+                if (g_verbose) {
+                    std::cerr << "Unknown KISS command: 0x" << std::hex << (int)cmd << std::dec << std::endl;
+                }
             }
         }
     }
@@ -444,7 +503,7 @@ private:
     void transmit(const std::vector<uint8_t>& data) {
         ui_log("TX: " + std::to_string(data.size()) + " bytes");
         if (g_verbose) {
-            hex_dump("TX", data.data(), data.size());
+            std::cerr << packet_visualize(data.data(), data.size(), true, config_.fragmentation_enabled) << std::endl;
         }
         
 #ifdef WITH_UI
@@ -593,9 +652,30 @@ private:
         
         std::vector<float> buffer(1024);
         int level_update_counter = 0;
-        const int LEVEL_UPDATE_INTERVAL = 5;  // Update level every N reads 
+        const int LEVEL_UPDATE_INTERVAL = 5;
         
-        auto frame_callback = [this](const uint8_t* data, size_t len) {
+        auto deliver_to_clients = [this](const std::vector<uint8_t>& payload, float snr, bool was_reassembled) {
+            ui_log("RX: " + std::to_string(payload.size()) + " bytes, SNR=" + 
+                   std::to_string((int)snr) + "dB" + (was_reassembled ? " (reassembled)" : ""));
+            if (g_verbose) {
+                std::cerr << packet_visualize(payload.data(), payload.size(), false, false) << std::endl;
+            }
+            
+#ifdef WITH_UI
+            if (g_ui_state) {
+                g_ui_state->add_packet(false, payload.size(), snr);
+            }
+#endif
+            
+            auto kiss_frame = KISSParser::wrap(payload);
+            
+            std::lock_guard<std::mutex> lock(clients_mutex_);
+            for (auto& client : clients_) {
+                client->send(kiss_frame);
+            }
+        };
+        
+        auto frame_callback = [this, &deliver_to_clients](const uint8_t* data, size_t len) {
             set_tx_lockout(RX_LOCKOUT_SECONDS);
             
             float snr = decoder_->get_last_snr();
@@ -608,7 +688,6 @@ private:
             }
 #endif
             
-            // Strip length prefix framing
             auto payload = unframe_length(data, len);
             
             if (payload.empty()) {
@@ -619,25 +698,18 @@ private:
                 return;
             }
             
-            ui_log("RX: " + std::to_string(payload.size()) + " bytes, SNR=" + 
-                   std::to_string((int)snr) + "dB");
-            if (g_verbose) {
-                hex_dump("RX", payload.data(), payload.size());
-            }
-            
-#ifdef WITH_UI
-            // Track packet for UI display
-            if (g_ui_state) {
-                g_ui_state->add_packet(false, payload.size(), snr);
-            }
-#endif
-            
-            // Send to all clients
-            auto kiss_frame = KISSParser::wrap(payload);
-            
-            std::lock_guard<std::mutex> lock(clients_mutex_);
-            for (auto& client : clients_) {
-                client->send(kiss_frame);
+            if (config_.fragmentation_enabled && reassembler_.is_fragment(payload)) {
+                if (g_verbose) {
+                    std::cerr << packet_visualize(payload.data(), payload.size(), false, true) << std::endl;
+                }
+                
+                auto reassembled = reassembler_.process(payload);
+                if (!reassembled.empty()) {
+                    ui_log("RX: Reassembled " + std::to_string(reassembled.size()) + " bytes from fragments");
+                    deliver_to_clients(reassembled, snr, true);
+                }
+            } else {
+                deliver_to_clients(payload, snr, false);
             }
         };
         
@@ -737,10 +809,13 @@ private:
     std::atomic<bool> tx_running_{false};
     std::atomic<bool> rx_running_{false};
     
+    Fragmenter fragmenter_;
+    Reassembler reassembler_;
+    
     // TX lockout - prevents TX while receiving
     std::mutex lockout_mutex_;
     std::chrono::steady_clock::time_point tx_lockout_until_;
-    static constexpr float RX_LOCKOUT_SECONDS = 0.5f;  // Post-RX settling time
+    static constexpr float RX_LOCKOUT_SECONDS = 0.5f;
     
 public:
     // Update config at runtime (called from UI)
@@ -810,10 +885,19 @@ public:
         return false;
     }
     
-    // Queue data for transmission 
     void queue_data(const std::vector<uint8_t>& data) {
-        auto framed = frame_with_length(data);
-        tx_queue_.push(framed);
+        size_t max_payload = payload_size_ - 2;
+        
+        if (config_.fragmentation_enabled && fragmenter_.needs_fragmentation(data.size(), max_payload)) {
+            auto fragments = fragmenter_.fragment(data, max_payload);
+            ui_log("TX: Fragmenting " + std::to_string(data.size()) + " bytes into " + 
+                   std::to_string(fragments.size()) + " fragments");
+            for (auto& frag : fragments) {
+                tx_queue_.push(std::move(frag));
+            }
+        } else {
+            tx_queue_.push(data);
+        }
 #ifdef WITH_UI
         if (g_ui_state) {
             g_ui_state->tx_queue_size = tx_queue_.size();
@@ -850,6 +934,9 @@ void print_help(const char* prog) {
               << "  --csma-threshold DB     Carrier sense threshold (default: -30)\n"
               << "  --csma-slot MS          Slot time in ms (default: 500)\n"
               << "  --csma-persist N        P-persistence 0-255 (default: 128 = 50%)\n"
+              << "\nFragmentation:\n"
+              << "  --frag                  Enable packet fragmentation/reassembly\n"
+              << "  --no-frag               Disable fragmentation (default)\n"
               << "\n"
 #ifdef WITH_UI
               << "  -h, --headless          Run without TUI\n"
@@ -948,6 +1035,10 @@ int main(int argc, char** argv) {
             config.slot_time_ms = std::atoi(argv[++i]);
         } else if (arg == "--csma-persist" && i + 1 < argc) {
             config.p_persistence = std::atoi(argv[++i]);
+        } else if (arg == "--frag") {
+            config.fragmentation_enabled = true;
+        } else if (arg == "--no-frag") {
+            config.fragmentation_enabled = false;
         } else {
             std::cerr << "Unknown option: " << arg << std::endl;
             print_help(argv[0]);
@@ -1005,6 +1096,7 @@ int main(int argc, char** argv) {
                 config.carrier_threshold_db = ui_state.carrier_threshold_db;
                 config.slot_time_ms = ui_state.slot_time_ms;
                 config.p_persistence = ui_state.p_persistence;
+                config.fragmentation_enabled = ui_state.fragmentation_enabled;
                 // Audio devices
                 config.audio_input_device = ui_state.audio_input_device;
                 config.audio_output_device = ui_state.audio_output_device;
@@ -1048,6 +1140,7 @@ int main(int argc, char** argv) {
                 ui_state.slot_time_ms = config.slot_time_ms;
                 ui_state.p_persistence = config.p_persistence;
                 ui_state.short_frame = config.short_frame;
+                ui_state.fragmentation_enabled = config.fragmentation_enabled;
                 // Audio devices
                 ui_state.audio_input_device = config.audio_input_device;
                 ui_state.audio_output_device = config.audio_output_device;
@@ -1099,8 +1192,8 @@ int main(int argc, char** argv) {
 
         ui_state.load_presets();
         
-
-
+        // Sync fragmentation setting from command line to UI
+        ui_state.fragmentation_enabled = config.fragmentation_enabled;
 
         ui_state.update_modem_info();
         
@@ -1111,6 +1204,40 @@ int main(int argc, char** argv) {
     }
 #endif
     
+    while (!check_port_available(config.bind_address, config.port)) {
+        std::cerr << "Error: Port " << config.port << " is already in use or cannot be bound" << std::endl;
+        std::cerr << "Another instance of modem73 may be running, or another application is using this port." << std::endl;
+        
+        if (!g_use_ui) {
+            std::cerr << "Use --port to specify a different port." << std::endl;
+            return 1;
+        }
+        
+        std::cerr << "\nEnter a different port number (or 'q' to quit): ";
+        std::string input;
+        if (!std::getline(std::cin, input) || input.empty() || input == "q" || input == "Q") {
+            std::cerr << "Exiting." << std::endl;
+            return 1;
+        }
+        
+        try {
+            int new_port = std::stoi(input);
+            if (new_port < 1 || new_port > 65535) {
+                std::cerr << "Invalid port number. Must be between 1 and 65535." << std::endl;
+                continue;
+            }
+            config.port = new_port;
+#ifdef WITH_UI
+            if (g_use_ui) {
+                ui_state.port = new_port;
+            }
+#endif
+            std::cerr << "Trying port " << config.port << "..." << std::endl;
+        } catch (const std::exception&) {
+            std::cerr << "Invalid input. Please enter a number." << std::endl;
+        }
+    }
+    
     try {
         KISSTNC tnc(config);
         
@@ -1127,6 +1254,7 @@ int main(int argc, char** argv) {
                 new_config.carrier_threshold_db = state.carrier_threshold_db;
                 new_config.p_persistence = state.p_persistence;
                 new_config.slot_time_ms = state.slot_time_ms;
+                new_config.fragmentation_enabled = state.fragmentation_enabled;
                 // Audio devices 
                 new_config.audio_input_device = state.audio_input_device;
                 new_config.audio_output_device = state.audio_output_device;

kiss_tnc.hh

@@ -3,10 +3,13 @@
 #include <cstdint>
 #include <vector>
 #include <queue>
+#include <map>
 #include <mutex>
 #include <atomic>
+#include <chrono>
 #include <functional>
 #include <string>
+#include <sstream>
 #include <iomanip>
 #include <iostream>
 
@@ -83,9 +86,12 @@ struct TNCConfig {
     
     // CSMA settings
     bool csma_enabled = true;
-    float carrier_threshold_db = -30.0f;  // Carrier sense threshold
-    int carrier_sense_ms = 100;           // How long to listen
-    int max_backoff_slots = 10;           // Maximum backoff
+    float carrier_threshold_db = -30.0f;
+    int carrier_sense_ms = 100;
+    int max_backoff_slots = 10;
+    
+    // Fragmentation settings
+    bool fragmentation_enabled = false;
     
     // Settings file path
     std::string config_file = "";
@@ -129,7 +135,6 @@ private:
     void process_byte(uint8_t byte) {
         if (byte == KISS::FEND) {
             if (in_frame_ && buffer_.size() > 0) {
-                // frame complete
                 uint8_t cmd_byte = buffer_[0];
                 uint8_t port = (cmd_byte >> 4) & 0x0F;
                 uint8_t cmd = cmd_byte & 0x0F;
@@ -206,7 +211,6 @@ inline void hex_dump(const char* prefix, const uint8_t* data, size_t len) {
     for (size_t i = 0; i < len; i += 16) {
         std::cerr << "  " << std::hex << std::setfill('0') << std::setw(4) << i << ": ";
         
-        // Hex
         for (size_t j = 0; j < 16 && i + j < len; ++j) {
             std::cerr << std::setw(2) << (int)data[i + j] << " ";
         }
@@ -214,7 +218,6 @@ inline void hex_dump(const char* prefix, const uint8_t* data, size_t len) {
             std::cerr << "   ";
         }
         
-        // ASCII
         std::cerr << " |";
         for (size_t j = 0; j < 16 && i + j < len; ++j) {
             char c = data[i + j];
@@ -225,6 +228,135 @@ inline void hex_dump(const char* prefix, const uint8_t* data, size_t len) {
     std::cerr << std::dec;
 }
 
+inline std::string packet_visualize(const uint8_t* data, size_t len, bool is_tx, bool frag_enabled) {
+    std::ostringstream oss;
+    
+    if (len == 0) {
+        oss << "  [EMPTY PACKET]";
+        return oss.str();
+    }
+    
+    oss << "\n  ┌─────────────────────────────────────────────────────────────┐\n";
+    oss << "  │ " << (is_tx ? "TX" : "RX") << " PACKET: " << len << " bytes";
+    oss << std::string(47 - std::to_string(len).length(), ' ') << "│\n";
+    oss << "  ├─────────────────────────────────────────────────────────────┤\n";
+    
+    size_t offset = 0;
+    
+    // Check for fragment by magic byte
+    if (frag_enabled && len >= 5 && data[0] == 0xF3) {
+        uint16_t pkt_id = (data[1] << 8) | data[2];
+        uint8_t seq = data[3];
+        uint8_t flags = data[4];
+        
+        oss << "  │ FRAG HDR [5 bytes]  Magic: 0xF3                             │\n";
+        oss << "  │   Packet ID: " << std::setw(5) << pkt_id;
+        oss << "   Seq: " << std::setw(3) << (int)seq;
+        oss << "   Flags: ";
+        
+        std::string flag_str;
+        if (flags & 0x02) flag_str += "FIRST ";
+        if (flags & 0x01) flag_str += "MORE";
+        if (flag_str.empty()) flag_str = "LAST";
+        oss << std::left << std::setw(12) << flag_str << std::right << "   │\n";
+        
+        offset = 5;
+        oss << "  ├─────────────────────────────────────────────────────────────┤\n";
+    }
+    
+    size_t payload_len = len - offset;
+    oss << "  │ PAYLOAD [" << payload_len << " bytes]";
+    oss << std::string(49 - std::to_string(payload_len).length(), ' ') << "│\n";
+    
+    size_t preview_len = std::min(payload_len, (size_t)32);
+    if (preview_len > 0) {
+        oss << "  │   ";
+        for (size_t i = 0; i < preview_len; i++) {
+            oss << std::hex << std::setfill('0') << std::setw(2) << (int)data[offset + i];
+            if (i < preview_len - 1) oss << " ";
+        }
+        if (payload_len > 32) oss << "...";
+        size_t used = preview_len * 3 - 1 + (payload_len > 32 ? 3 : 0);
+        if (used < 57) oss << std::string(57 - used, ' ');
+        oss << std::dec << " │\n";
+        
+        oss << "  │   ";
+        for (size_t i = 0; i < preview_len; i++) {
+            char c = data[offset + i];
+            oss << (c >= 32 && c < 127 ? c : '.');
+        }
+        if (payload_len > 32) oss << "...";
+        size_t ascii_used = preview_len + (payload_len > 32 ? 3 : 0);
+        if (ascii_used < 57) oss << std::string(57 - ascii_used, ' ');
+        oss << " │\n";
+    }
+    
+    oss << "  └─────────────────────────────────────────────────────────────┘";
+    
+    return oss.str();
+}
+
+inline std::string kiss_frame_visualize(const uint8_t* data, size_t len) {
+    std::ostringstream oss;
+    
+    if (len == 0) {
+        oss << "  [EMPTY KISS FRAME]";
+        return oss.str();
+    }
+    
+    oss << "\n  ┌─────────────────────────────────────────────────────────────┐\n";
+    oss << "  │ KISS FRAME: " << len << " bytes";
+    oss << std::string(45 - std::to_string(len).length(), ' ') << "│\n";
+    oss << "  ├─────────────────────────────────────────────────────────────┤\n";
+    
+    if (len >= 1) {
+        uint8_t cmd_byte = data[0];
+        uint8_t port = (cmd_byte >> 4) & 0x0F;
+        uint8_t cmd = cmd_byte & 0x0F;
+        
+        oss << "  │ CMD BYTE: 0x" << std::hex << std::setfill('0') << std::setw(2) << (int)cmd_byte << std::dec;
+        oss << "  Port: " << (int)port << "  Cmd: ";
+        
+        std::string cmd_name;
+        switch (cmd) {
+            case 0x00: cmd_name = "DATA"; break;
+            case 0x01: cmd_name = "TXDELAY"; break;
+            case 0x02: cmd_name = "P"; break;
+            case 0x03: cmd_name = "SLOTTIME"; break;
+            case 0x04: cmd_name = "TXTAIL"; break;
+            case 0x05: cmd_name = "FULLDUPLEX"; break;
+            case 0x06: cmd_name = "SETHW"; break;
+            case 0x0F: cmd_name = "RETURN"; break;
+            default: cmd_name = "UNKNOWN"; break;
+        }
+        oss << std::left << std::setw(10) << cmd_name << std::right;
+        oss << "              │\n";
+    }
+    
+    if (len > 1) {
+        oss << "  ├─────────────────────────────────────────────────────────────┤\n";
+        size_t payload_len = len - 1;
+        oss << "  │ PAYLOAD [" << payload_len << " bytes]";
+        oss << std::string(49 - std::to_string(payload_len).length(), ' ') << "│\n";
+        
+        size_t preview_len = std::min(payload_len, (size_t)24);
+        oss << "  │   ";
+        for (size_t i = 0; i < preview_len; i++) {
+            oss << std::hex << std::setfill('0') << std::setw(2) << (int)data[1 + i];
+            if (i < preview_len - 1) oss << " ";
+        }
+        if (payload_len > 24) oss << " ...";
+        oss << std::dec;
+        size_t used = preview_len * 3 - 1 + (payload_len > 24 ? 4 : 0);
+        if (used < 57) oss << std::string(57 - used, ' ');
+        oss << " │\n";
+    }
+    
+    oss << "  └─────────────────────────────────────────────────────────────┘";
+    
+    return oss.str();
+}
+
 // Length-prefix framing 
 // This handles OFDM frame padding where the payload is encoded within the 2 byte prefix
 inline std::vector<uint8_t> frame_with_length(const std::vector<uint8_t>& data) {
@@ -246,3 +378,171 @@ inline std::vector<uint8_t> unframe_length(const uint8_t* data, size_t total_len
     }
     return std::vector<uint8_t>(data + 2, data + 2 + payload_len);
 }
+
+namespace Frag {
+    constexpr uint8_t MAGIC = 0xF3;
+    constexpr size_t HEADER_SIZE = 5;
+    constexpr uint8_t FLAG_MORE_FRAGMENTS = 0x01;
+    constexpr uint8_t FLAG_FIRST_FRAGMENT = 0x02;
+    constexpr int REASSEMBLY_TIMEOUT_MS = 30000;
+    constexpr size_t MAX_PENDING_PACKETS = 64;
+}
+
+class Fragmenter {
+public:
+    Fragmenter() : next_packet_id_(0) {}
+    
+    std::vector<std::vector<uint8_t>> fragment(const std::vector<uint8_t>& data, size_t max_payload) {
+        std::vector<std::vector<uint8_t>> fragments;
+        
+        if (max_payload <= Frag::HEADER_SIZE) {
+            return fragments;
+        }
+        
+        size_t data_per_frag = max_payload - Frag::HEADER_SIZE;
+        size_t num_frags = (data.size() + data_per_frag - 1) / data_per_frag;
+        if (num_frags > 255) {
+            num_frags = 255;
+        }
+        
+        uint16_t packet_id = next_packet_id_++;
+        
+        for (size_t i = 0; i < num_frags; i++) {
+            size_t offset = i * data_per_frag;
+            size_t chunk_size = std::min(data_per_frag, data.size() - offset);
+            
+            std::vector<uint8_t> frag;
+            frag.reserve(Frag::HEADER_SIZE + chunk_size);
+            
+            frag.push_back(Frag::MAGIC);
+            frag.push_back((packet_id >> 8) & 0xFF);
+            frag.push_back(packet_id & 0xFF);
+            frag.push_back(static_cast<uint8_t>(i));
+            
+            uint8_t flags = 0;
+            if (i == 0) flags |= Frag::FLAG_FIRST_FRAGMENT;
+            if (i < num_frags - 1) flags |= Frag::FLAG_MORE_FRAGMENTS;
+            frag.push_back(flags);
+            
+            frag.insert(frag.end(), data.begin() + offset, data.begin() + offset + chunk_size);
+            fragments.push_back(std::move(frag));
+        }
+        
+        return fragments;
+    }
+    
+    bool needs_fragmentation(size_t data_size, size_t max_payload) const {
+        return data_size > (max_payload - Frag::HEADER_SIZE);
+    }
+    
+private:
+    std::atomic<uint16_t> next_packet_id_;
+};
+
+class Reassembler {
+public:
+    Reassembler() = default;
+    
+    std::vector<uint8_t> process(const std::vector<uint8_t>& fragment) {
+        if (fragment.size() < Frag::HEADER_SIZE) {
+            return {};
+        }
+        
+        if (fragment[0] != Frag::MAGIC) {
+            return {};
+        }
+        
+        uint16_t packet_id = (fragment[1] << 8) | fragment[2];
+        uint8_t seq = fragment[3];
+        uint8_t flags = fragment[4];
+        
+        std::vector<uint8_t> payload(fragment.begin() + Frag::HEADER_SIZE, fragment.end());
+        
+        std::lock_guard<std::mutex> lock(mutex_);
+        
+        cleanup_stale();
+        
+        auto& pkt = pending_[packet_id];
+        if (pkt.fragments.empty()) {
+            pkt.first_seen = std::chrono::steady_clock::now();
+        }
+        
+        pkt.fragments[seq] = std::move(payload);
+        
+        if (flags & Frag::FLAG_FIRST_FRAGMENT) {
+            pkt.has_first = true;
+        }
+        
+        if (!(flags & Frag::FLAG_MORE_FRAGMENTS)) {
+            pkt.last_seq = seq;
+            pkt.has_last = true;
+        }
+        
+        if (pkt.has_first && pkt.has_last) {
+            bool complete = true;
+            for (uint8_t i = 0; i <= pkt.last_seq; i++) {
+                if (pkt.fragments.find(i) == pkt.fragments.end()) {
+                    complete = false;
+                    break;
+                }
+            }
+            
+            if (complete) {
+                std::vector<uint8_t> reassembled;
+                for (uint8_t i = 0; i <= pkt.last_seq; i++) {
+                    auto& frag_data = pkt.fragments[i];
+                    reassembled.insert(reassembled.end(), frag_data.begin(), frag_data.end());
+                }
+                pending_.erase(packet_id);
+                return reassembled;
+            }
+        }
+        
+        return {};
+    }
+    
+    bool is_fragment(const std::vector<uint8_t>& data) const {
+        if (data.size() < Frag::HEADER_SIZE) return false;
+        return data[0] == Frag::MAGIC;
+    }
+    
+    void reset() {
+        std::lock_guard<std::mutex> lock(mutex_);
+        pending_.clear();
+    }
+    
+private:
+    struct PendingPacket {
+        std::map<uint8_t, std::vector<uint8_t>> fragments;
+        std::chrono::steady_clock::time_point first_seen;
+        uint8_t last_seq = 0;
+        bool has_first = false;
+        bool has_last = false;
+    };
+    
+    void cleanup_stale() {
+        auto now = std::chrono::steady_clock::now();
+        for (auto it = pending_.begin(); it != pending_.end();) {
+            auto age = std::chrono::duration_cast<std::chrono::milliseconds>(
+                now - it->second.first_seen).count();
+            if (age > Frag::REASSEMBLY_TIMEOUT_MS) {
+                it = pending_.erase(it);
+            } else {
+                ++it;
+            }
+        }
+        
+        while (pending_.size() > Frag::MAX_PENDING_PACKETS) {
+            auto oldest = pending_.begin();
+            for (auto it = pending_.begin(); it != pending_.end(); ++it) {
+                if (it->second.first_seen < oldest->second.first_seen) {
+                    oldest = it;
+                }
+            }
+            pending_.erase(oldest);
+        }
+    }
+    
+    std::map<uint16_t, PendingPacket> pending_;
+    mutable std::mutex mutex_;
+};

tnc_ui.hh

@@ -91,6 +91,8 @@ struct TNCUIState {
     int mtu_bytes = 0;
     int bitrate_bps = 0;
     float airtime_seconds = 0.0f;
+    int random_data_size = 0;
+    bool fragmentation_enabled = false;
     
     // stats
     std::atomic<float> total_tx_time{0.0f};  
@@ -269,6 +271,13 @@ struct TNCUIState {
             bitrate_bps = bitrate_normal[mod][rate];
             airtime_seconds = duration_normal[mod] / 1000.0f;
         }
+        
+        // Initialize random_data_size if not set, clamp to MTU only if fragmentation disabled
+        if (random_data_size == 0) {
+            random_data_size = mtu_bytes;
+        } else if (!fragmentation_enabled && random_data_size > mtu_bytes) {
+            random_data_size = mtu_bytes;
+        }
     }
     
     void update_level(float db) {
@@ -345,6 +354,7 @@ struct TNCUIState {
         fprintf(f, "carrier_threshold_db=%.1f\n", carrier_threshold_db);
         fprintf(f, "slot_time_ms=%d\n", slot_time_ms);
         fprintf(f, "p_persistence=%d\n", p_persistence);
+        fprintf(f, "fragmentation_enabled=%d\n", fragmentation_enabled ? 1 : 0);
         fprintf(f, "# Audio/PTT\n");
         fprintf(f, "audio_input=%s\n", audio_input_device.c_str());
         fprintf(f, "audio_output=%s\n", audio_output_device.c_str());
@@ -359,6 +369,8 @@ struct TNCUIState {
         fprintf(f, "com_invert_rts=%d\n", com_invert_rts ? 1 : 0);
         fprintf(f, "# Network\n");
         fprintf(f, "port=%d\n", port);
+        fprintf(f, "# Utils\n");
+        fprintf(f, "random_data_size=%d\n", random_data_size);
         
         fclose(f);
         return true;
@@ -386,6 +398,7 @@ struct TNCUIState {
                 else if (strcmp(key, "carrier_threshold_db") == 0) carrier_threshold_db = atof(value);
                 else if (strcmp(key, "slot_time_ms") == 0) slot_time_ms = atoi(value);
                 else if (strcmp(key, "p_persistence") == 0) p_persistence = atoi(value);
+                else if (strcmp(key, "fragmentation_enabled") == 0) fragmentation_enabled = atoi(value) != 0;
                 else if (strcmp(key, "audio_input") == 0) audio_input_device = value;
                 else if (strcmp(key, "audio_output") == 0) audio_output_device = value;
                 else if (strcmp(key, "audio_device") == 0) {
@@ -401,6 +414,7 @@ struct TNCUIState {
                 else if (strcmp(key, "com_invert_dtr") == 0) com_invert_dtr = atoi(value) != 0;
                 else if (strcmp(key, "com_invert_rts") == 0) com_invert_rts = atoi(value) != 0;
                 else if (strcmp(key, "port") == 0) port = atoi(value);
+                else if (strcmp(key, "random_data_size") == 0) random_data_size = atoi(value);
             }
         }
         
@@ -657,7 +671,8 @@ private:
         FIELD_FREQ,
         FIELD_CSMA,
         FIELD_THRESHOLD,
-        FIELD_PERSISTENCE,  
+        FIELD_PERSISTENCE,
+        FIELD_FRAGMENTATION,
         FIELD_AUDIO_INPUT,
         FIELD_AUDIO_OUTPUT,
         FIELD_PTT_TYPE,
@@ -747,6 +762,11 @@ private:
                     } else if (current_field_ >= FIELD_MODULATION && current_field_ != FIELD_PRESET) {
                         adjust_field(-1);
                     }
+                } else if (current_tab_ == 3 && (utils_selection_ == 0 || utils_selection_ == 1)) {
+                    int step = 1;
+                    if (state_.random_data_size >= 1000) step = 100;
+                    else if (state_.random_data_size >= 100) step = 10;
+                    state_.random_data_size = std::max(1, state_.random_data_size - step);
                 }
                 break;
                 
@@ -763,6 +783,12 @@ private:
                     } else if (current_field_ >= FIELD_MODULATION && current_field_ != FIELD_PRESET) {
                         adjust_field(1);
                     }
+                } else if (current_tab_ == 3 && (utils_selection_ == 0 || utils_selection_ == 1)) {
+                    int step = 1;
+                    if (state_.random_data_size >= 1000) step = 100;
+                    else if (state_.random_data_size >= 100) step = 10;
+                    int max_size = state_.fragmentation_enabled ? 65535 : state_.mtu_bytes;
+                    state_.random_data_size = std::min(max_size, state_.random_data_size + step);
                 }
                 break;
                 
@@ -1112,6 +1138,11 @@ private:
                 state_.p_persistence += delta * 8;
                 state_.p_persistence = std::max(0, std::min(255, state_.p_persistence));
                 break;
+            case FIELD_FRAGMENTATION:
+                state_.fragmentation_enabled = !state_.fragmentation_enabled;
+                state_.update_modem_info();  // Update random_data_size limits
+                state_.add_log("(!) Fragmentation changed, restart required");
+                break;
             case FIELD_AUDIO_INPUT:
                 break;
             case FIELD_AUDIO_OUTPUT:
@@ -2115,6 +2146,20 @@ private:
         }
         row += 2;
         
+        // Fragmentation section
+        dy = visible_y(row);
+        if (dy >= 0) {
+            attron(A_DIM);
+            mvaddstr(dy, c1, "FRAGMENTATION");
+            mvaddstr(dy, c1 + 14, "(restart)");
+            attroff(A_DIM);
+        }
+        row++;
+        
+        dy = visible_y(row);
+        if (dy >= 0) draw_toggle_field(dy, c1, c2, "Enabled", FIELD_FRAGMENTATION, state_.fragmentation_enabled);
+        row += 2;
+        
         // Audio / ptt
 
         dy = visible_y(row);
@@ -2625,28 +2670,56 @@ private:
         
         y++;
         
-        // Test info
         attron(COLOR_PAIR(4) | A_BOLD);
         mvaddstr(y, c1, "[ TEST INFO ]");
         attroff(COLOR_PAIR(4) | A_BOLD);
         y++;
         
         attron(A_DIM);
-        mvaddstr(y, c1, "Payload");
+        mvaddstr(y, c1, "MTU");
         attroff(A_DIM);
-        mvprintw(y, c1 + 12, "%d bytes", state_.mtu_bytes);
+        mvprintw(y, c1 + 14, "%d bytes", state_.mtu_bytes);
+        if (state_.fragmentation_enabled) {
+            attron(COLOR_PAIR(4));
+            printw(" [FRAG]");
+            attroff(COLOR_PAIR(4));
+        }
+        y++;
+        
+        bool size_selected = (utils_selection_ == 0 || utils_selection_ == 1);
+        if (size_selected) {
+            attron(A_BOLD | COLOR_PAIR(4));
+        } else {
+            attron(A_DIM);
+        }
+        mvaddstr(y, c1, "Test Size");
+        if (size_selected) {
+            attroff(A_BOLD | COLOR_PAIR(4));
+            mvprintw(y, c1 + 14, "< %d bytes >", state_.random_data_size);
+        } else {
+            attroff(A_DIM);
+            mvprintw(y, c1 + 14, "%d bytes", state_.random_data_size);
+        }
+        
+        if (state_.fragmentation_enabled && state_.random_data_size > state_.mtu_bytes) {
+            int data_per_frag = state_.mtu_bytes - 5;  // 5-byte fragment header
+            int num_frags = (state_.random_data_size + data_per_frag - 1) / data_per_frag;
+            attron(COLOR_PAIR(3));
+            printw(" (%d frags)", num_frags);
+            attroff(COLOR_PAIR(3));
+        }
         y++;
         
         attron(A_DIM);
         mvaddstr(y, c1, "Pattern");
         attroff(A_DIM);
-        mvaddstr(y, c1 + 12, "0x55 (alternating)");
+        mvaddstr(y, c1 + 14, "0x55 (alternating)");
         y++;
         
         attron(A_DIM);
         mvaddstr(y, c1, "Frames Sent");
         attroff(A_DIM);
-        mvprintw(y, c1 + 12, "%d", state_.tx_frame_count.load());
+        mvprintw(y, c1 + 14, "%d", state_.tx_frame_count.load());
         y++;
         
         int ry = 4;
@@ -2704,29 +2777,26 @@ private:
     void handle_utils_action() {
         switch (utils_selection_) {
             case 0: {
-                // Send test pattern 
                 if (state_.on_send_data) {
-                    std::vector<uint8_t> data(state_.mtu_bytes, 0x55);
+                    std::vector<uint8_t> data(state_.random_data_size, 0x55);
                     state_.on_send_data(data);
-                    state_.add_log("Sent test pattern (" + std::to_string(state_.mtu_bytes) + " bytes)");
+                    state_.add_log("Sent test pattern (" + std::to_string(state_.random_data_size) + " bytes)");
                 }
                 break;
             }
             case 1: {
-                // Send random data
                 if (state_.on_send_data) {
-                    std::vector<uint8_t> data(state_.mtu_bytes);
+                    std::vector<uint8_t> data(state_.random_data_size);
                     std::random_device rd;
                     std::mt19937 gen(rd());
                     std::uniform_int_distribution<> dis(0, 255);
                     for (auto& b : data) b = dis(gen);
                     state_.on_send_data(data);
-                    state_.add_log("Sent random data (" + std::to_string(state_.mtu_bytes) + " bytes)");
+                    state_.add_log("Sent random data (" + std::to_string(state_.random_data_size) + " bytes)");
                 }
                 break;
             }
             case 2: {
-                // Send ping 
                 if (state_.on_send_data) {
                     std::string ping = "PING:" + state_.callsign;
                     std::vector<uint8_t> data(ping.begin(), ping.end());

update.sh

@@ -0,0 +1,112 @@
+#!/usr/bin/env bash
+#
+# modem73 update script
+# https://github.com/RFnexus/modem73
+#
+
+set -e
+
+REPO_URL="https://github.com/RFnexus/modem73.git"
+INSTALL_DIR="${MODEM73_DIR:-$HOME/modem73}"
+
+if [ -t 1 ]; then
+    RED='\033[0;31m'
+    GREEN='\033[0;32m'
+    YELLOW='\033[1;33m'
+    NC='\033[0m'
+else
+    RED=''
+    GREEN=''
+    YELLOW=''
+    NC=''
+fi
+
+info()  { echo -e "${GREEN}[INFO]${NC} $1"; }
+warn()  { echo -e "${YELLOW}[WARN]${NC} $1"; }
+error() { echo -e "${RED}[ERROR]${NC} $1"; exit 1; }
+
+command -v git >/dev/null 2>&1 || error "git is required but not installed"
+command -v make >/dev/null 2>&1 || error "make is required but not installed"
+
+
+if command -v g++ >/dev/null 2>&1; then
+    CXX="g++"
+elif command -v clang++ >/dev/null 2>&1; then
+    CXX="clang++"
+else
+    error "C++ compiler (g++ or clang++) is required but not installed"
+fi
+
+info "modem73 updater"
+echo "  Repository: $REPO_URL"
+echo "  Install to: $INSTALL_DIR"
+echo ""
+
+if [ -d "$INSTALL_DIR/.git" ]; then
+    info "Updating = installation..."
+    cd "$INSTALL_DIR"
+    
+    if ! git diff --quiet 2>/dev/null; then
+        warn "Local changes detected. Stashing..."
+        git stash
+    fi
+    
+    BRANCH=$(git rev-parse --abbrev-ref HEAD)
+    
+    git fetch origin
+    LOCAL=$(git rev-parse HEAD)
+    REMOTE=$(git rev-parse "origin/$BRANCH")
+    
+    if [ "$LOCAL" = "$REMOTE" ]; then
+        info "Already up to date"
+        NEEDS_BUILD=0
+    else
+        info "Pulling updates..."
+        git pull --ff-only origin "$BRANCH"
+        NEEDS_BUILD=1
+    fi
+else
+    info "Cloning repository..."
+    mkdir -p "$(dirname "$INSTALL_DIR")"
+    git clone "$REPO_URL" "$INSTALL_DIR"
+    cd "$INSTALL_DIR"
+    NEEDS_BUILD=1
+fi
+
+# Build
+if [ "${NEEDS_BUILD:-1}" = "1" ] || [ "$1" = "--force" ]; then
+    info "Building modem73..."
+
+
+
+    make clean 2>/dev/null || true
+    
+
+
+    if make -j"$(nproc 2>/dev/null || echo 2)"; then
+        info "Build sucessful!"
+        
+
+
+
+        echo ""
+        echo "  Commit: $(git rev-parse --short HEAD)"
+        echo "  Date:   $(git log -1 --format=%ci)"
+        echo ""
+        
+
+
+
+        if [ -f "$INSTALL_DIR/modem73" ]; then
+            info "Binary: $INSTALL_DIR/modem73"
+        fi
+    else
+        error "Build failed"
+    fi
+else
+    info "No build needed (use --force to rebuild)"
+fi
+
+
+
+info "Done!"