README.md

@@ -104,7 +104,7 @@ partial, alternate, and planned behavior.
 | `-c, --checksum` | Verify content by checksum instead of size+mtime |
 | `-z, --compress [level]` | Enable streaming zstd compression (level 1–22, default 5) |
 | `-a, --archive` | rsync archive mode (`-rlptgoD`): links, metadata, devices and specials (not compression/multithreading) |
-| `-j, --threads` | Multithreading mode |
+| `-j, --threads[=N]` | Multithreading mode; `N` (1–256) sets the parallel scanner worker count, bare `-j`/`--threads` uses the default |
 | `-m` | rsync `--prune-empty-dirs` (short form now rsync-parity) |
 | `--chunk-serialization` | Chunk serialization (batch all files per chunk; long form only) |
 | `-s` | rsync `--secluded-args` compatibility no-op (remote SSH argv is already injection-safe) |
@@ -202,7 +202,7 @@ transfer is never aborted.
 3. **FileMetadata** — `mode`, `uid`, `gid`, `mtime_sec`, `mtime_nsec`;
 uid / gid are advisory wire fields and are never applied by the receiver;
 atime is unsupported
-4. **Config** — runtime parameters (transported over wire, TLS settings excluded). Includes `timeout`, `contimeout`, `quiet`, `backup`, `backup_dir`, `stats`, `max_depth`, `log_file`, `queue_size`.
+4. **Config** — runtime parameters (transported over wire, TLS settings excluded). Includes `timeout`, `contimeout`, `quiet`, `backup`, `backup_dir`, `stats`, `max_depth`, `log_file`.
 5. **Queue** — thread-safe bounded queue with condition variables
 6. **DirectoryScanner** — recursive BFS traversal with exclude and include pattern support, max-depth enforcement
 
@@ -378,7 +378,7 @@ features without changing the meaning of ordinary compatibility options.
 
 | Option | Purpose |
 |---|---|
-| `-j`, `--threads` | Enable the multithreaded scanner/loader/sender pipeline. |
+| `-j`, `--threads[=N]` | Enable the multithreaded scanner/loader/sender pipeline. `N` (1–256) sets the parallel scanner worker count; bare `-j`/`--threads` uses the default. |
 | `-z [level]`, `--compress [level]` | Enable streaming zstd compression, levels 1-22. |
 | `--compress-level <n>` | Set the zstd compression level. |
 | `--zc <alg>` | Alias for `--compress-choice`. FastSync supports `zstd` and `none`. |
@@ -392,7 +392,7 @@ features without changing the meaning of ordinary compatibility options.
 | `--delta-block <bytes>` | Set the FastSync delta block size (`--block-size` is an alias). |
 | `--delta-max <bytes>` | Limit files eligible for FastSync delta transfer. |
 | `--server-host <host>` | Select the TCP server host. |
-| `--server-port <port>` | Select the TCP server port. |
+| `--server-port <port>` | Select the TCP server port (`--port <port>` and `--port=<port>` are rsync-friendly aliases). |
 | `--tls` | Enable TLS for TCP transport. |
 | `--bwlimit <KB/s>` | Apply token-bucket bandwidth limiting. |
 | `--progress` | Show transfer progress and throughput. |
@@ -478,7 +478,7 @@ link-target transfer remains incomplete. |
 | `--dest-dir <path>` | Set the destination directory explicitly. |
 | `--save-to-disk` | Enable server-side disk persistence. |
 | `--server-host <host>` | TCP server address. |
-| `--server-port <port>` | TCP server port. |
+| `--server-port <port>` | TCP server port. `--port <port>` / `--port=<port>` is an alias. |
 | `--tls` | Enable TLS. Requires `--cert` and `--key`. |
 | `--cert <path>` | TLS certificate file. |
 | `--key <path>` | TLS private key file. |

RSYNC_COMPAT.md

@@ -612,7 +612,7 @@ now transmits targets (the prior behavior was broken/partial); its status moved
 |------|-------------------|-----------------|-------|
 | `-e`, `--rsh=COMMAND` | Remote shell to use | ✅ Implemented | `-e`/`--rsh` (and `--rsh=COMMAND`) select the remote-shell program used to build the SSH child argv, overriding the default `ssh`. The command is whitespace-split into the leading argv words so rsync's `-e "ssh -p 2222"` works; the standard `-o` family, an optional `-p` port, `user@host` and the quoted remote command (`fastsync-server --stdio`) follow. Stored in the `rsh_command` config field. **Client-only, never crosses the wire** (it is a launch concern, not a handshake property) |
 | `--rsync-path=PROGRAM` | rsync binary on remote | ✅ Implemented | Alias for `--fastsync-server-path`: both write the `fastsync_server_path` config field used as the remote-side server program (always quoted as one remote-shell word), which CROSSES the wire as before. Kept separate from `--rsh`, which names the local connecting program |
-| `--port=PORT` | Alternate daemon port | ✅ Implemented | rsync's daemon-port flag maps to the client-side `server_port` config field: a client connects to a TCP/TLS server (incl. `host::module/path` daemon destinations) with `--server-port`, and the `fastsync-server --daemon` listener's port is taken from its config's `port` key (default 873) or overridden by `--dparam port=` / `-p` |
+| `--port=PORT`, `--port PORT` | Alternate daemon port | ✅ Implemented | rsync's daemon-port flag is an alias for `--server-port`: both spellings (and `--server-port=PORT`) map to the client-side `server_port` config field. The client connects to a TCP/TLS server (incl. `host::module/path` daemon destinations) on that port, and the `fastsync-server --daemon` listener's port is taken from its config's `port` key (default 873) or overridden by `--dparam port=` / `-p` |
 | `--sockopts=OPTIONS` | Custom TCP options | ✅ Implemented | Comma-separated allowlist of `OPT=VAL` applied via `setsockopt` after `socket()` before `connect()`/`bind()`. Only `TCP_NODELAY`, `SO_KEEPALIVE`, `SO_REUSEADDR` (0/1) and `SO_RCVBUF`/`SO_SNDBUF` (byte count) are accepted; an unknown option name or a bad value is rejected up front, never silently ignored. A value is required for every option (`OPT=VAL`; a bare name is an error). Applied to the outgoing TCP and TLS client socket; absent by default. `SockOptEntry`/`sockopts` config fields. Local socket concern: never crosses the wire |
 | `--blocking-io` | Use blocking I/O for remote shell | ✅ Implemented | With `--blocking-io` the SSH-transport socketpair socket is left without `SO_RCVTIMEO`/`SO_SNDTIMEO`, so the transfer blocks naturally; by default it gets the same read/write timeout as the TCP transport (see `--timeout`). `blocking_io` config bool. **Client-only, never crosses the wire** |
 | `--outbuf=N\|L\|B` | Set output buffering | ✅ Implemented | `N` (none/unbuffered) → `_IONBF`, `L` (line) → `_IOLBF`, `B` (block, the default) → `_IOFBF` via `setvbuf` on stdout and stderr. Garbage values are rejected. `outbuf` config field (`OutbufMode`). **Client-only, never crosses the wire** |
@@ -893,7 +893,7 @@ Ranked by user demand, implementation complexity, and interoperability impact (_
 
 | Feature | Description |
 |---------|-------------|
-| `-j` / `--threads` | Multithreaded pipeline (scanner/loader/sender) (renamed from `-m` in Phase 7 Wave A; `-m` is now rsync `--prune-empty-dirs`) |
+| `-j` / `--threads[=N]` | Multithreaded pipeline (scanner/loader/sender); `N` (1–256) sizes the parallel scanner worker pool, bare `-j`/`--threads` uses the built-in default (renamed from `-m` in Phase 7 Wave A; `-m` is now rsync `--prune-empty-dirs`) |
 | `--chunk-serialization` | Chunk serialization mode (long form only; `-s` is now rsync `--secluded-args`) |
 | `--sendfile` | Zero-copy sendfile() syscall (TCP only) (long form only; `-f` is now rsync `--filter`) |
 | `-z [level]` / `--compress` | zstd compression level (1-22) (`-c` is now rsync `--checksum`) |

src/client/client_cli.c

@@ -12,6 +12,7 @@
 #include "identity.h"
 #include "log.h"
 #include "protocol.h"
+#include "scanner.h"
 #include "stop_condition.h"
 #include "transport_tcp.h"
 #include "transport_tls.h"
@@ -27,6 +28,26 @@
 #include <stdlib.h>
 #include <string.h>
 
+/* Async-signal-safe abort flag set by the SIGINT/SIGTERM handler.  Exposed via
+ * client_send.h so the send loops can poll it.  Defined here (not in
+ * client_send.c) so the unit-test binary, which compiles this file but not
+ * client_send.c, still links the symbol. */
+volatile sig_atomic_t client_abort_requested = 0;
+
+#ifndef FASTSYNC_TEST_BUILD
+/* Signal handler: perform NO work beyond storing the flag.  Logging, protocol
+ * I/O and the STATUS_ABORT frame are all done later on the normal send path,
+ * which is not async-signal-safe.  Only the production client installs it. */
+static void client_signal_handler(int signo) {
+  (void)signo;
+  client_abort_requested = 1;
+}
+#endif
+
+bool client_abort_pending(void) {
+  return client_abort_requested != 0;
+}
+
 #ifndef FASTSYNC_TEST_BUILD
 /* Parse environment variables for source/destination directories and save-to-disk flag. */
 static void parse_environment(const char** out_env_source, const char** out_env_dest,
@@ -141,6 +162,23 @@ static int set_checksum_seed(Config* config, const char* value) {
   return 0;
 }
 
+/* --threads=N: enable the -m pipeline and size its parallel scanner pool.
+ * Rejects a non-positive, non-numeric or oversized value up front. */
+static int set_scanner_threads_option(Config* config, const char* value) {
+  int threads;
+  if (!parse_positive_int(value, &threads)) {
+    log_message(LOG_LEVEL_ERROR, "--threads must be a positive integer");
+    return -1;
+  }
+  if (threads > MAX_SCANNER_THREADS) {
+    log_message(LOG_LEVEL_ERROR, "--threads must be between 1 and %d", MAX_SCANNER_THREADS);
+    return -1;
+  }
+  config->use_multithreading = true;
+  config->scanner_threads = threads;
+  return 0;
+}
+
 static int set_compression_threads_option(int* dest, const char* value) {
   if (set_positive_int_option(dest, value, "--compress-threads") != 0)
     return -1;
@@ -1288,10 +1326,21 @@ static bool cli_handle_transfer_flags(CliParseCtx* ctx) {
     return true;
   }
   if (opt_is(arg, "-j", "--threads")) {
+    /* Bare -j/--threads: enable the pipeline with the scanner's built-in
+       worker default (scanner_threads stays 0). */
     config->use_multithreading = true;
     log_info_message(LOG_INFO_MISC, "Enabled Multithreading");
     return true;
   }
+  if (strncmp(arg, "--threads=", 10) == 0) {
+    if (set_scanner_threads_option(config, arg + 10) != 0) {
+      ctx->exit_code = -1;
+    } else {
+      log_info_message(LOG_INFO_MISC, "Enabled Multithreading with %d scanner threads",
+                       config->scanner_threads);
+    }
+    return true;
+  }
   if (opt_is(arg, "--chunk-serialization", NULL)) {
     config->use_chunk_serialization = true;
     log_info_message(LOG_INFO_MISC, "Enabled Chunk Serialization");
@@ -1300,29 +1349,48 @@ static bool cli_handle_transfer_flags(CliParseCtx* ctx) {
   return false;
 }
 
-/* Network/IO options: --server-port, --bwlimit, --chunk-size, --log-file and
- * --stderr.  Returns true when the argument was consumed. */
+/* Parse and validate a TCP server port (--server-port, or its rsync-friendly
+ * alias --port).  Returns 0 on success, -1 (with a message) on a malformed or
+ * out-of-range value. */
+static int set_server_port_option(Config* config, const char* value, const char* option_name) {
+  int port;
+  if (!parse_positive_int(value, &port)) {
+    char* escaped = output_escape(value, false);
+    log_message(LOG_LEVEL_ERROR, "invalid %s value: %s", option_name,
+                escaped ? escaped : "<allocation failed>");
+    free(escaped);
+    return -1;
+  }
+  if (port > 65535) {
+    log_message(LOG_LEVEL_ERROR, "server port must be 1-65535");
+    return -1;
+  }
+  config->server_port = port;
+  return 0;
+}
+
+/* Network/IO options: --server-port/--port, --bwlimit, --chunk-size, --log-file
+ * and --stderr.  Returns true when the argument was consumed. */
 static bool cli_handle_io_options(CliParseCtx* ctx) {
   Config* config = ctx->config;
   const char* arg = ctx->argv[ctx->i];
-  if (opt_is(arg, "--server-port", NULL)) {
+  if (opt_is(arg, "--server-port", "--port")) {
     if (ctx->i + 1 >= ctx->argc) {
       log_message(LOG_LEVEL_ERROR, "missing argument for %s", arg);
       ctx->exit_code = -1;
       return true;
     }
-    if (!parse_positive_int(ctx->argv[++ctx->i], &config->server_port)) {
-      char* escaped = output_escape(ctx->argv[ctx->i], false);
-      log_message(LOG_LEVEL_ERROR, "invalid --server-port value: %s",
-                  escaped ? escaped : "<allocation failed>");
-      free(escaped);
+    if (set_server_port_option(config, ctx->argv[++ctx->i], arg) != 0)
       ctx->exit_code = -1;
     return true;
   }
-    if (config->server_port > 65535) {
-      log_message(LOG_LEVEL_ERROR, "server port must be 1-65535");
+  /* rsync users commonly write --port=NNNN; --server-port=NNNN is accepted too
+   * so both spellings behave identically. */
+  if (strncmp(arg, "--server-port=", 14) == 0 || strncmp(arg, "--port=", 7) == 0) {
+    const char* option_name = strncmp(arg, "--server-port=", 14) == 0 ? "--server-port" : "--port";
+    const char* value = arg + (strncmp(arg, "--server-port=", 14) == 0 ? 14 : 7);
+    if (set_server_port_option(config, value, option_name) != 0)
       ctx->exit_code = -1;
-    }
     return true;
   }
   if (opt_is(arg, "--bwlimit", NULL)) {
@@ -1975,6 +2043,17 @@ int main(int argc, char* argv[]) {
      oversized delta).  Ignore SIGPIPE so that a broken TCP connection
      surfaces as a clean write error instead of killing the client. */
   signal(SIGPIPE, SIG_IGN);
+  /* Ctrl-C / SIGTERM: set the abort flag so the send loops can send
+   * STATUS_ABORT and let the receiver clean up, instead of dying abruptly.
+   * No SA_RESTART so an in-flight poll()/read() is interrupted (EINTR), which
+   * lets the keepalive/abort checks observe the flag promptly. */
+  struct sigaction abort_action;
+  memset(&abort_action, 0, sizeof(abort_action));
+  abort_action.sa_handler = client_signal_handler;
+  sigemptyset(&abort_action.sa_mask);
+  abort_action.sa_flags = 0;
+  sigaction(SIGINT, &abort_action, NULL);
+  sigaction(SIGTERM, &abort_action, NULL);
   const char* env_source = NULL;
   const char* env_dest = NULL;
   bool save_to_disk = false;

src/client/client_send.c

@@ -885,6 +885,10 @@ static int send_delete_manifest(int fd, ArrayList* manifest, ArrayList* protecte
    unlinks) before replying, so the wait uses a generous explicit deadline
    instead of the default 60 s receive window. */
 #define DELETE_ACK_TIMEOUT_SEC 3600
+/* While waiting for the (potentially slow) receiver-side deletion, send a
+ * STATUS_KEEPALIVE at most this often so the connection is demonstrably alive
+ * and neither side's per-message timeout trips. */
+#define DELETE_ACK_KEEPALIVE_SEC 10
 
 static bool send_delete_manifest_early(Client* client, ArrayList* manifest,
                                        ArrayList* protected_prefixes, ArrayList* missing_args) {
@@ -894,8 +898,21 @@ static bool send_delete_manifest_early(Client* client, ArrayList* manifest,
       0)
     return false;
   Status ack;
-  if (!receive_status_timed(client->file_descriptor, &ack, DELETE_ACK_TIMEOUT_SEC))
+  /* The wait is long (up to an hour) and runs inline on this thread: a helper
+   * thread would race the non-thread-safe protocol send path, so keepalives are
+   * emitted from this wait loop itself.  A Ctrl-C/SIGTERM abort flag also ends
+   * the wait; the caller then best-effort sends STATUS_ABORT. */
+  if (!receive_status_keepalive(client->file_descriptor, &ack, DELETE_ACK_TIMEOUT_SEC,
+                                DELETE_ACK_KEEPALIVE_SEC, client_abort_pending)) {
+    /* A Ctrl-C/SIGTERM abort ends the wait above; tell the receiver before the
+       caller tears the connection down (best-effort). */
+    if (client_abort_pending()) {
+      log_info_message(LOG_INFO_MISC,
+                       "Abort requested while awaiting delete ack; sending STATUS_ABORT");
+      send_status(client->file_descriptor, STATUS_ABORT);
+    }
     return false;
+  }
   if (ack != STATUS_OK) {
     log_message(LOG_LEVEL_ERROR, "Server failed to delete files before the transfer");
     return false;
@@ -1490,6 +1507,19 @@ static int send_chunks_multithreaded(void* pipeline_context) {
   }
 
   while (true) {
+    /* Graceful abort (Ctrl-C/SIGTERM): tell the receiver to clean up instead of
+       dying abruptly.  Best-effort: a failed send just means the peer is gone.
+       Only reached while the session is active (config_send already succeeded). */
+    if (client_abort_pending()) {
+      log_info_message(LOG_INFO_MISC,
+                       "Abort requested; sending STATUS_ABORT to server and disconnecting");
+      send_status(client->file_descriptor, STATUS_ABORT);
+      pipeline_cancel(context);
+      disconnect_transfer_client(client);
+      mark_sender_done(context);
+      protocol_session_unbind();
+      return thrd_error;
+    }
     /* Phase 6: stop-elegantly at the next chunk boundary once the --stop-after
        / --stop-at deadline has passed.  Everything already sent is finalized by
        the completion tail below; the run still returns success. */
@@ -1624,7 +1654,9 @@ static int scan_directory_multithreaded(void* pipeline_context) {
   PipelineContextSender* context = (PipelineContextSender*)pipeline_context;
   protocol_session_bind(&context->allocation_session);
   PreparedScanner prepared;
-  if (!prepare_scanner(context->config, 4, &prepared)) {
+  /* -j/--threads=N sizes the parallel scanner's worker pool; 0 (bare -j) lets
+   * the scanner apply its built-in default. */
+  if (!prepare_scanner(context->config, context->config->scanner_threads, &prepared)) {
     pipeline_cancel(context);
     protocol_session_unbind();
     return thrd_error;
@@ -2036,6 +2068,15 @@ int send_files(Config* config) {
      only a prefix of the source. */
   bool scan_stopped_early = false;
   while ((current_chunk = directory_scanner_next(scanner)) != NULL) {
+    /* Graceful abort (Ctrl-C/SIGTERM): notify the receiver and clean up.  The
+       session is active (config_send already succeeded); a send failure here is
+       fine because the client is exiting anyway. */
+    if (client_abort_pending()) {
+      log_info_message(LOG_INFO_MISC, "Abort requested; sending STATUS_ABORT to server");
+      chunk_destroy(current_chunk);
+      send_status(client->file_descriptor, STATUS_ABORT);
+      goto send_fail;
+    }
     /* Phase 6: stop-elegantly at the next chunk boundary once the deadline has
        passed.  The scanner may also have stopped early itself; either way the
        completion tail below keeps everything already sent. */
@@ -2099,6 +2140,13 @@ int send_files(Config* config) {
     goto send_fail;
   if (directory_scanner_had_io_error(scanner))
     had_scan_io = true;
+  /* An abort that arrived after the last chunk must still stop the completion
+     tail (manifest/finalize) rather than let it run to success. */
+  if (client_abort_pending()) {
+    log_info_message(LOG_INFO_MISC, "Abort requested; sending STATUS_ABORT to server");
+    send_status(client->file_descriptor, STATUS_ABORT);
+    goto send_fail;
+  }
   /* Phase 6: the scanner may have stopped early (returning NULL without a
      failure) as soon as the deadline passed, so reflect that here too.  A
      deadline that cut the scan short leaves an incomplete keep-set; transmitting
@@ -2276,7 +2324,7 @@ int send_files_multithreaded(Config** config_ptr) {
          fills the protected excluded prefixes. */
       PreparedScanner prepared;
       memset(&prepared, 0, sizeof(prepared));
-      bool prepared_ok = prepare_scanner(config, 4, &prepared);
+      bool prepared_ok = prepare_scanner(config, config->scanner_threads, &prepared);
       if (prepared_ok && context->excluded_paths)
         prepared.options.excluded_paths = context->excluded_paths;
       bool prebuilt = prepared_ok && scan_paths_only(config, &prepared.options, context->manifest,

src/client/client_send.h

@@ -4,6 +4,15 @@
 #include "chunk.h"
 #include "config.h"
 #include "transport_tcp.h"
+#include <signal.h>
+#include <stdbool.h>
+
+/* Set ONLY by the client's SIGINT/SIGTERM handler (async-signal-safe: the
+ * handler stores 1 and does nothing else).  The send loops poll it via
+ * client_abort_pending() and, when set, best-effort send STATUS_ABORT so the
+ * receiver can clean up before the client exits. */
+extern volatile sig_atomic_t client_abort_requested;
+bool client_abort_pending(void);
 
 /* Both sender entry points BORROW `config` for the duration of the call; they
  * never free it, and the caller retains ownership (freeing it with

src/client/scanner.h

@@ -14,6 +14,10 @@
 #include <sys/types.h>
 #include <threads.h>
 
+/* Upper bound on the configurable parallel scanner worker count (--threads=N):
+ * keeps one transfer from spawning an unbounded pool on a very large machine. */
+#define MAX_SCANNER_THREADS 256
+
 typedef struct {
   bool use_metadata;
   /* Phase 4 metadata capture: -U/--atimes and -N/--crtimes tell the scanner to

src/client/usage.c

@@ -2,6 +2,7 @@
 #include <stdio.h>
 #include <delta.h>
 #include <chunk.h>
+#include "scanner.h"
 
 void print_usage(void) {
   printf("Usage:\n");
@@ -144,7 +145,10 @@ void print_usage(void) {
   printf("                    Delta block size in bytes (default: %d)\n", DELTA_BLOCK_SIZE_DEFAULT);
   printf("  --delta-max <n>     Max file size for delta transfer (default: %llu)\n",
          DELTA_MAX_FILE_SIZE);
-  printf("  -j, --threads       Enable multithreading\n");
+  printf("  -j, --threads[=N]   Enable the multithreaded scanner/loader/sender\n");
+  printf("                      pipeline; N (1-%d) sets the parallel scanner worker\n",
+         MAX_SCANNER_THREADS);
+  printf("                      count (bare -j/--threads uses the default)\n");
   printf("  --chunk-serialization  Enable chunk serialization (long form only)\n");
   printf("  -s, --secluded-args    Protect-args compatibility option (no effect; remote\n");
   printf("                      SSH argv is already built injection-safe)\n");
@@ -203,6 +207,7 @@ void print_usage(void) {
   printf("  --save-to-disk      Write received files to disk\n");
   printf("  --server-host <ip>  Server IP address (default: 127.0.0.1)\n");
   printf("  --server-port <n>   Server port (default: 8080)\n");
+  printf("  --port <n>          Alias for --server-port\n");
   printf("  --password-file <f> Authenticate a host::module/path daemon destination.\n");
   printf("                      The file's first user:password line supplies the\n");
   printf("                      username and password (only a SHA-256 digest of the\n");

src/shared/config.c

@@ -23,6 +23,7 @@ static void config_set_defaults(Config* config) {
   config->receive_root_directory = NULL;
   config->save_to_disk = false;
   config->use_multithreading = false;
+  config->scanner_threads = 0;
   config->use_chunk_serialization = false;
   config->use_compression = false;
   config->use_metadata = false;
@@ -79,7 +80,6 @@ static void config_set_defaults(Config* config) {
   config->stats = false;
   config->max_depth = 0;
   config->log_file = NULL;
-  config->queue_size = 100;
   config->follow_symlinks = false;
   config->partial = false;
   config->copy_links = false;
@@ -147,14 +147,11 @@ static void config_set_defaults(Config* config) {
   config->delete_during = false;
   config->delete_delay = false;
   config->address = NULL;
-  config->bind_address = NULL;
   config->ipv6 = false;
   config->ipv4 = false;
   config->sockopts = NULL;
   config->sockopt_count = 0;
   config->daemon = false;
-  config->daemon_config = NULL;
-  config->server_mode = false;
   config->no_motd = false;
   config->checksum = false;
   config->checksum_algo = CHECKSUM_ALGO_XXH64;
@@ -789,9 +786,7 @@ void config_delete(Config* config) {
   free(config->partial_dir);
   free(config->suffix);
   free(config->address);
-  free(config->bind_address);
   free(config->sockopts);
-  free(config->daemon_config);
   free(config->compress_choice);
   free(config->chmod_spec);
   if (config->skip_compress_suffixes) {

src/shared/config.h

@@ -81,6 +81,11 @@ typedef struct Config {
   char* receive_root_directory;
   bool save_to_disk;
   bool use_multithreading;
+  /* -j/--threads=N: number of parallel scanner worker threads for the -m
+   * pipeline.  0 (the default, also set by bare -j/--threads) means "use the
+   * scanner's built-in default" (4).  CLIENT-ONLY: it is a local scheduling
+   * concern and is NEVER serialized into the wire config frame. */
+  int scanner_threads;
   bool use_chunk_serialization;
   bool use_compression;
   bool use_sendfile;
@@ -170,7 +175,6 @@ typedef struct Config {
   bool stats;
   int max_depth;
   FILE* log_file;
-  int queue_size;
   bool follow_symlinks;
   bool partial;
 
@@ -348,21 +352,17 @@ typedef struct Config {
 
   // PR #181: IPv6 and bind address
   char* address;
-  char* bind_address;
   bool ipv6;
   bool ipv4;
   /* --sockopts=OPTIONS (Phase 5, Wave B): strict allowlist of TCP/socket
    * options applied via setsockopt after socket() and before connect()/bind().
    * These are LOCAL socket concerns: they never cross the wire config frame.
-   * .address is the outgoing/source bind address (--address); .bind_address is
-   * reserved for daemon-side binding and is not wired yet. */
+   * .address is the outgoing/source bind address (--address). */
   SockOptEntry* sockopts;
   int sockopt_count;
 
   // PR #182: Daemon/server mode
   bool daemon;
-  char* daemon_config;
-  bool server_mode;
   /* --no-motd (Wave C): CLIENT-ONLY, never crosses the wire.  Suppresses
    * DISPLAY of the daemon's MOTD; the daemon still sends the MOTD frame, so
    * the client reads and discards it to keep the stream in sync.  rsync's

src/shared/protocol.c

@@ -609,6 +609,136 @@ bool protocol_receive_status_timed(ProtocolSession* session, Status* status, int
   return true;
 }
 
+/* Read exactly one Status frame within `deadline` (CLOCK_MONOTONIC).  Unlike
+ * protocol_receive_status_keepalive this never emits a keepalive: it is used
+ * to consume the first byte(s) of an already-signalled frame and to drain the
+ * peer's outstanding keepalive replies, where injecting a write could split a
+ * reply across a frame boundary.  Returns false on timeout/EOF/error. */
+static bool protocol_read_status_until(ProtocolSession* session, Status* status,
+                                       const struct timespec* deadline) {
+  Status received = STATUS_ERROR;
+  size_t got = 0;
+  while (got < sizeof(Status)) {
+    if (!session->ssl || SSL_pending(session->ssl) == 0) {
+      int remaining_ms = deadline_remaining_ms(deadline);
+      if (remaining_ms <= 0) {
+        log_message(LOG_LEVEL_ERROR, "Receive timeout while reading status");
+        return false;
+      }
+      struct pollfd pfd = {.fd = session->read_fd, .events = POLLIN};
+      int poll_result = poll(&pfd, 1, remaining_ms);
+      if (poll_result == 0) {
+        log_message(LOG_LEVEL_ERROR, "Receive timeout while reading status");
+        return false;
+      }
+      if (poll_result < 0) {
+        if (errno == EINTR)
+          continue;
+        return false;
+      }
+      if (pfd.revents & (POLLERR | POLLNVAL))
+        return false;
+    }
+    ssize_t bytes_received;
+    if (session->ssl)
+      bytes_received = SSL_read(session->ssl, (char*)&received + got, sizeof(Status) - got);
+    else
+      bytes_received = read(session->read_fd, (char*)&received + got, sizeof(Status) - got);
+    if (bytes_received <= 0) {
+      if (session->ssl) {
+        int ssl_err = SSL_get_error(session->ssl, (int)bytes_received);
+        if (ssl_err == SSL_ERROR_WANT_READ || ssl_err == SSL_ERROR_WANT_WRITE)
+          continue;
+      }
+      if (bytes_received < 0 && errno == EINTR)
+        continue;
+      log_message(LOG_LEVEL_ERROR, "Connection closed while receiving status");
+      return false;
+    }
+    got += (size_t)bytes_received;
+  }
+  *status = received;
+  return true;
+}
+
+bool protocol_receive_status_keepalive(ProtocolSession* session, Status* status, int timeout_sec,
+                                       int keepalive_interval_sec, ProtocolWaitAbort abort_check) {
+  if (!session || !status)
+    return false;
+  if (timeout_sec <= 0)
+    timeout_sec = RECEIVE_TIMEOUT_SEC;
+  if (keepalive_interval_sec <= 0)
+    keepalive_interval_sec = timeout_sec;
+
+  struct timespec deadline;
+  clock_gettime(CLOCK_MONOTONIC, &deadline);
+  deadline.tv_sec += timeout_sec;
+
+  unsigned long keepalives_sent = 0;
+  unsigned long replies_seen = 0;
+  Status final = STATUS_ERROR;
+  while (true) {
+    if (abort_check && abort_check())
+      return false;
+    if (!session->ssl || SSL_pending(session->ssl) == 0) {
+      int remaining_ms = deadline_remaining_ms(&deadline);
+      if (remaining_ms <= 0) {
+        log_message(LOG_LEVEL_ERROR, "Receive timeout after %ds", timeout_sec);
+        return false;
+      }
+      /* Only interleave a keepalive while waiting for the FIRST byte of a
+       * frame; once part of a frame is buffered a write could race the peer's
+       * reply into the middle of it. */
+      int interval_ms = keepalive_interval_sec * 1000;
+      int wait_ms = interval_ms < remaining_ms ? interval_ms : remaining_ms;
+      struct pollfd pfd = {.fd = session->read_fd, .events = POLLIN};
+      int poll_result = poll(&pfd, 1, wait_ms);
+      if (poll_result == 0) {
+        if (abort_check && abort_check())
+          return false;
+        if (!protocol_send_status(session, STATUS_KEEPALIVE))
+          return false;
+        keepalives_sent++;
+        continue;
+      }
+      if (poll_result < 0) {
+        if (errno == EINTR)
+          continue;
+        return false;
+      }
+      if (pfd.revents & (POLLERR | POLLNVAL))
+        return false;
+    }
+    Status received;
+    if (!protocol_read_status_until(session, &received, &deadline))
+      return false;
+    if (received == STATUS_KEEPALIVE) {
+      /* The receiver's answer to one of our keepalives. */
+      replies_seen++;
+      continue;
+    }
+    final = received;
+    break;
+  }
+  /* Drain the replies the receiver still owes for keepalives we sent while it
+   * was busy.  It answers them only after the real status, so leaving them
+   * unread would put stale KEEPALIVE frames ahead of the next exchange and
+   * desynchronize the protocol. */
+  while (replies_seen < keepalives_sent) {
+    Status drained;
+    if (!protocol_read_status_until(session, &drained, &deadline))
+      return false;
+    if (drained != STATUS_KEEPALIVE) {
+      log_message(LOG_LEVEL_ERROR, "Unexpected status while draining keepalive replies");
+      return false;
+    }
+    replies_seen++;
+  }
+  *status = final;
+  log_debug_message(LOG_DEBUG_PROTO, "Received Status: %s", status_to_string(*status));
+  return true;
+}
+
 bool send_str(int fd, const char* data) {
   return protocol_send_str(legacy_session(-1, fd), data);
 }
@@ -648,3 +778,8 @@ bool receive_status(int fd, Status* status) {
 bool receive_status_timed(int fd, Status* status, int timeout_sec) {
   return protocol_receive_status_timed(legacy_session(fd, -1), status, timeout_sec);
 }
+bool receive_status_keepalive(int fd, Status* status, int timeout_sec, int keepalive_interval_sec,
+                              ProtocolWaitAbort abort_check) {
+  return protocol_receive_status_keepalive(legacy_session(fd, -1), status, timeout_sec,
+                                           keepalive_interval_sec, abort_check);
+}

src/shared/protocol.h

@@ -198,4 +198,23 @@ bool receive_status(int file_descriptor, Status* status);
    this so the sender does not abort after the deletion already committed. */
 bool receive_status_timed(int file_descriptor, Status* status, int timeout_sec);
 
+/* Callback polled by protocol_receive_status_keepalive once per keepalive
+   interval.  Return true to stop waiting (e.g. a SIGINT/SIGTERM abort flag was
+   set).  Kept as a function pointer so the protocol layer does not depend on
+   client signal state. */
+typedef bool (*ProtocolWaitAbort)(void);
+
+/* Like receive_status_timed, but while the peer is silent it emits
+   STATUS_KEEPALIVE every keepalive_interval_sec (the receiver answers each with
+   STATUS_KEEPALIVE, which this function consumes and skips) so a long
+   server-side operation does not look like a dead connection.  The total wait
+   is still bounded by timeout_sec; abort_check (may be NULL) is polled every
+   interval and, when it returns true, ends the wait immediately with false.
+   Runs entirely on the calling thread: the protocol send path is NOT safe for
+   concurrent writers, so this must not be paired with a helper thread. */
+bool receive_status_keepalive(int file_descriptor, Status* status, int timeout_sec,
+                              int keepalive_interval_sec, ProtocolWaitAbort abort_check);
+bool protocol_receive_status_keepalive(ProtocolSession* session, Status* status, int timeout_sec,
+                                       int keepalive_interval_sec, ProtocolWaitAbort abort_check);
+
 #endif

tests/test_client_cli.c

@@ -1,5 +1,6 @@
 #include "test_client_cli.h"
 #include "checksum.h"
+#include "client_send.h"
 #include "client_validation.h"
 #include "chmod.h"
 #include "config.h"
@@ -579,6 +580,80 @@ static void test_parse_args_invalid_server_port() {
   config_delete(cfg);
 }
 
+/* --port is a documented rsync-style alias for --server-port; both the
+ * two-argument and the inline "=" spellings must work. */
+static void test_parse_args_port_alias() {
+  Config* cfg = config_create();
+  char* argv_space[] = {"fastsync", "--port", "9000", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+  EXPECT_EQ_INT(parse_args(cfg, 5, argv_space, positional_args, &positional_count), 0);
+  EXPECT_EQ_INT(cfg->server_port, 9000);
+  config_delete(cfg);
+
+  cfg = config_create();
+  char* argv_inline[] = {"fastsync", "--port=9001", "/src", "/dst"};
+  positional_count = 0;
+  EXPECT_EQ_INT(parse_args(cfg, 4, argv_inline, positional_args, &positional_count), 0);
+  EXPECT_EQ_INT(cfg->server_port, 9001);
+  config_delete(cfg);
+
+  cfg = config_create();
+  char* argv_long[] = {"fastsync", "--server-port=9002", "/src", "/dst"};
+  positional_count = 0;
+  EXPECT_EQ_INT(parse_args(cfg, 4, argv_long, positional_args, &positional_count), 0);
+  EXPECT_EQ_INT(cfg->server_port, 9002);
+  config_delete(cfg);
+}
+
+/* --threads=N sizes the pipeline scanner; bare -j/--threads keeps the default
+ * (scanner_threads == 0), and invalid values are rejected. */
+static void test_parse_args_threads() {
+  Config* cfg = config_create();
+  char* argv_eq[] = {"fastsync", "--threads=8", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+  EXPECT_EQ_INT(parse_args(cfg, 4, argv_eq, positional_args, &positional_count), 0);
+  EXPECT_TRUE(cfg->use_multithreading);
+  EXPECT_EQ_INT(cfg->scanner_threads, 8);
+  config_delete(cfg);
+
+  cfg = config_create();
+  char* argv_short[] = {"fastsync", "-j", "/src", "/dst"};
+  positional_count = 0;
+  EXPECT_EQ_INT(parse_args(cfg, 4, argv_short, positional_args, &positional_count), 0);
+  EXPECT_TRUE(cfg->use_multithreading);
+  EXPECT_EQ_INT(cfg->scanner_threads, 0);
+  config_delete(cfg);
+
+  cfg = config_create();
+  char* argv_long[] = {"fastsync", "--threads", "/src", "/dst"};
+  positional_count = 0;
+  EXPECT_EQ_INT(parse_args(cfg, 4, argv_long, positional_args, &positional_count), 0);
+  EXPECT_TRUE(cfg->use_multithreading);
+  EXPECT_EQ_INT(cfg->scanner_threads, 0);
+  config_delete(cfg);
+
+  const char* bad[] = {"--threads=0", "--threads=-3", "--threads=abc", "--threads=257"};
+  for (size_t i = 0; i < sizeof(bad) / sizeof(bad[0]); i++) {
+    cfg = config_create();
+    char* argv_bad[] = {"fastsync", (char*)bad[i], "/src", "/dst"};
+    positional_count = 0;
+    EXPECT_EQ_INT(parse_args(cfg, 4, argv_bad, positional_args, &positional_count), -1);
+    config_delete(cfg);
+  }
+}
+
+/* The graceful-abort flag is a plain sig_atomic_t toggled by the handler. */
+static void test_client_abort_flag() {
+  client_abort_requested = 0;
+  EXPECT_FALSE(client_abort_pending());
+  client_abort_requested = 1;
+  EXPECT_TRUE(client_abort_pending());
+  client_abort_requested = 0;
+  EXPECT_FALSE(client_abort_pending());
+}
+
 /* Test parse_args rejects invalid compression level (-z/--compress) */
 static void test_parse_args_invalid_compression_level() {
   Config* cfg = config_create();
@@ -3224,6 +3299,9 @@ void test_client_cli() {
   test_parse_args_invalid_port();
   test_parse_args_non_numeric_port();
   test_parse_args_invalid_server_port();
+  test_parse_args_port_alias();
+  test_parse_args_threads();
+  test_client_abort_flag();
   test_parse_args_invalid_compression_level();
   test_parse_args_valid_compression_level();
   test_parse_args_debug_flags();

tests/test_protocol.c

@@ -460,6 +460,96 @@ static void test_send_receive_status_timed() {
   close(p[0]);
 }
 
+static bool keepalive_always_abort(void) {
+  return true;
+}
+
+/* A pre-buffered KEEPALIVE reply from the peer must be consumed transparently,
+   leaving the first real status visible to the caller. */
+static void test_receive_status_keepalive_skips_reply() {
+  int p[2];
+  EXPECT_EQ_INT(pipe(p), 0);
+  ProtocolSession session;
+  protocol_session_init(&session, p[0], p[1]);
+
+  EXPECT_TRUE(protocol_send_status(&session, STATUS_KEEPALIVE));
+  EXPECT_TRUE(protocol_send_status(&session, STATUS_OK));
+
+  Status received = STATUS_ERROR;
+  EXPECT_TRUE(protocol_receive_status_keepalive(&session, &received, 5, 1, NULL));
+  EXPECT_EQ_INT((int)received, (int)STATUS_OK);
+
+  close(p[0]);
+  close(p[1]);
+}
+
+/* The abort callback ends the wait immediately, before any keepalive traffic. */
+static void test_receive_status_keepalive_aborts() {
+  int p[2];
+  EXPECT_EQ_INT(pipe(p), 0);
+  ProtocolSession session;
+  protocol_session_init(&session, p[0], p[1]);
+
+  Status received = STATUS_ERROR;
+  EXPECT_FALSE(
+      protocol_receive_status_keepalive(&session, &received, 5, 1, keepalive_always_abort));
+
+  close(p[0]);
+  close(p[1]);
+}
+
+typedef struct {
+  int peer_read_fd;
+  int peer_write_fd;
+  bool replied;
+} KeepalivePeerArg;
+
+static int keepalive_peer(void* arg) {
+  KeepalivePeerArg* peer = arg;
+  ProtocolSession session;
+  protocol_session_init(&session, peer->peer_read_fd, peer->peer_write_fd);
+  Status status = STATUS_ERROR;
+  if (protocol_receive_status(&session, &status) && status == STATUS_KEEPALIVE) {
+    /* Model the busy receiver: it sends the real ack first, then the keepalive
+       reply it owes for the queued keepalive (which the client must drain so it
+       does not desynchronize the stream). */
+    peer->replied = protocol_send_status(&session, STATUS_OK) &&
+                    protocol_send_status(&session, STATUS_KEEPALIVE);
+  }
+  return thrd_success;
+}
+
+/* While the peer is silent the helper must emit STATUS_KEEPALIVE, then consume
+   the peer's ack and drain the keepalive reply that follows it -- proving the
+   inline keepalive loop works without a second writer racing the send path. */
+static void test_receive_status_keepalive_emits() {
+  int to_client[2];
+  int to_peer[2];
+  EXPECT_EQ_INT(pipe(to_client), 0);
+  EXPECT_EQ_INT(pipe(to_peer), 0);
+
+  ProtocolSession session;
+  protocol_session_init(&session, to_client[0], to_peer[1]);
+
+  KeepalivePeerArg peer = {.peer_read_fd = to_peer[0], .peer_write_fd = to_client[1]};
+  thrd_t thread;
+  EXPECT_EQ_INT(thrd_create(&thread, keepalive_peer, &peer), thrd_success);
+
+  Status received = STATUS_ERROR;
+  EXPECT_TRUE(protocol_receive_status_keepalive(&session, &received, 10, 1, NULL));
+  EXPECT_EQ_INT((int)received, (int)STATUS_OK);
+
+  int result = 0;
+  EXPECT_EQ_INT(thrd_join(thread, &result), thrd_success);
+  EXPECT_EQ_INT(result, thrd_success);
+  EXPECT_TRUE(peer.replied);
+
+  close(to_client[0]);
+  close(to_client[1]);
+  close(to_peer[0]);
+  close(to_peer[1]);
+}
+
 void test_protocol() {
   test_send_receive_n_data();
   test_send_receive_n_data_zero();
@@ -471,6 +561,9 @@ void test_protocol() {
   test_send_receive_status();
   test_protocol_session_io_timeout();
   test_send_receive_status_timed();
+  test_receive_status_keepalive_skips_reply();
+  test_receive_status_keepalive_aborts();
+  test_receive_status_keepalive_emits();
   test_receive_n_data_truncated();
   test_receive_str_truncated();
   test_max_alloc_rejects_single_buffer();