tests: add the mqtt test server mqttd

4 files changed, 1001 insertions, 7 deletions

diff --git a/tests/server/Makefile.inc b/tests/server/Makefile.inc
index a865ee509..fb13d79cb 100644
--- a/tests/server/Makefile.inc
+++ b/tests/server/Makefile.inc
@@ -20,7 +20,8 @@
 #
 ###########################################################################
 
-noinst_PROGRAMS = getpart resolve rtspd sockfilt sws tftpd fake_ntlm socksd disabled
+noinst_PROGRAMS = getpart resolve rtspd sockfilt sws tftpd fake_ntlm    \
+ socksd disabled mqttd
 
 CURLX_SRCS = \
  ../../lib/mprintf.c \
@@ -78,6 +79,12 @@ socksd_SOURCES = $(CURLX_SRCS) $(CURLX_HDRS) $(USEFUL) $(UTIL) \
 socksd_LDADD = @CURL_NETWORK_AND_TIME_LIBS@
 socksd_CFLAGS = $(AM_CFLAGS)
 
+mqttd_SOURCES = $(CURLX_SRCS) $(CURLX_HDRS) $(USEFUL) $(UTIL) \
+ server_sockaddr.h mqttd.c \
+ ../../lib/inet_pton.c
+mqttd_LDADD = @CURL_NETWORK_AND_TIME_LIBS@
+mqttd_CFLAGS = $(AM_CFLAGS)
+
 sws_SOURCES = $(CURLX_SRCS) $(CURLX_HDRS) $(USEFUL) $(UTIL) \
  server_sockaddr.h \
  sws.c \
diff --git a/tests/server/mqttd.c b/tests/server/mqttd.c
new file mode 100644
index 000000000..435df69a1
--- /dev/null
+++ b/tests/server/mqttd.c
@@ -0,0 +1,977 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+#include "server_setup.h"
+#include <stdlib.h>
+#include <string.h>
+#include "util.h"
+
+/* Function
+ *
+ * Accepts a TCP connection on a custom port (IPv4 or IPv6).  Speaks MQTT.
+ *
+ * Read commands from FILE (set with --config). The commands control how to
+ * act and is reset to defaults each client TCP connect.
+ *
+ * Config file keywords:
+ *
+ * TODO
+ */
+
+/* based on sockfilt.c */
+
+#ifdef HAVE_SIGNAL_H
+#include <signal.h>
+#endif
+#ifdef HAVE_NETINET_IN_H
+#include <netinet/in.h>
+#endif
+#ifdef HAVE_NETINET_IN6_H
+#include <netinet/in6.h>
+#endif
+#ifdef HAVE_ARPA_INET_H
+#include <arpa/inet.h>
+#endif
+#ifdef HAVE_NETDB_H
+#include <netdb.h>
+#endif
+
+#define ENABLE_CURLX_PRINTF
+/* make the curlx header define all printf() functions to use the curlx_*
+   versions instead */
+#include "curlx.h" /* from the private lib dir */
+#include "getpart.h"
+#include "inet_pton.h"
+#include "util.h"
+#include "server_sockaddr.h"
+#include "warnless.h"
+
+/* include memdebug.h last */
+#include "memdebug.h"
+
+#ifdef USE_WINSOCK
+#undef  EINTR
+#define EINTR    4 /* errno.h value */
+#undef  EAGAIN
+#define EAGAIN  11 /* errno.h value */
+#undef  ENOMEM
+#define ENOMEM  12 /* errno.h value */
+#undef  EINVAL
+#define EINVAL  22 /* errno.h value */
+#endif
+
+#define DEFAULT_PORT 1883 /* MQTT default port */
+
+#ifndef DEFAULT_LOGFILE
+#define DEFAULT_LOGFILE "log/mqttd.log"
+#endif
+
+#ifndef DEFAULT_CONFIG
+#define DEFAULT_CONFIG "mqttd.config"
+#endif
+
+#define MQTT_MSG_CONNECT    0x10
+#define MQTT_MSG_CONNACK    0x20
+#define MQTT_MSG_PUBLISH    0x30
+#define MQTT_MSG_PUBACK     0x40
+#define MQTT_MSG_SUBSCRIBE  0x82
+#define MQTT_MSG_SUBACK     0x90
+#define MQTT_MSG_DISCONNECT 0xe0
+
+#define MQTT_CONNACK_LEN 4
+#define MQTT_SUBACK_LEN 5
+#define MQTT_CLIENTID_LEN 12 /* "curl0123abcd" */
+#define MQTT_HEADER_LEN 5    /* max 5 bytes */
+
+struct configurable {
+  unsigned char version; /* initial version byte in the request must match
+                            this */
+};
+
+#define REQUEST_DUMP  "log/server.input"
+#define CONFIG_VERSION 5
+
+static struct configurable config;
+
+const char *serverlogfile = DEFAULT_LOGFILE;
+static const char *configfile = DEFAULT_CONFIG;
+
+#ifdef ENABLE_IPV6
+static bool use_ipv6 = FALSE;
+#endif
+static const char *ipv_inuse = "IPv4";
+static unsigned short port = DEFAULT_PORT;
+
+static void resetdefaults(void)
+{
+  logmsg("Reset to defaults");
+  config.version = CONFIG_VERSION;
+}
+
+static unsigned char byteval(char *value)
+{
+  unsigned long num = strtoul(value, NULL, 10);
+  return num & 0xff;
+}
+
+static void getconfig(void)
+{
+  FILE *fp = fopen(configfile, FOPEN_READTEXT);
+  resetdefaults();
+  if(fp) {
+    char buffer[512];
+    logmsg("parse config file");
+    while(fgets(buffer, sizeof(buffer), fp)) {
+      char key[32];
+      char value[32];
+      if(2 == sscanf(buffer, "%31s %31s", key, value)) {
+        if(!strcmp(key, "version")) {
+          config.version = byteval(value);
+          logmsg("version [%d] set", config.version);
+        }
+      }
+    }
+    fclose(fp);
+  }
+}
+
+static void loghex(unsigned char *buffer, ssize_t len)
+{
+  char data[12000];
+  ssize_t i;
+  unsigned char *ptr = buffer;
+  char *optr = data;
+  ssize_t width = 0;
+  int left = sizeof(data);
+
+  for(i = 0; i<len && (left >= 0); i++) {
+    msnprintf(optr, left, "%02x", ptr[i]);
+    width += 2;
+    optr += 2;
+    left -= 2;
+  }
+  if(width)
+    logmsg("'%s'", data);
+}
+
+typedef enum {
+  FROM_CLIENT,
+  FROM_SERVER
+} mqttdir;
+
+static void logprotocol(mqttdir dir,
+                        const char *prefix, size_t remlen,
+                        FILE *output,
+                        unsigned char *buffer, ssize_t len)
+{
+  char data[12000] = "";
+  ssize_t i;
+  unsigned char *ptr = buffer;
+  char *optr = data;
+  ssize_t width = 0;
+  int left = sizeof(data);
+
+  for(i = 0; i<len && (left >= 0); i++) {
+    msnprintf(optr, left, "%02x", ptr[i]);
+    width += 2;
+    optr += 2;
+    left -= 2;
+  }
+  fprintf(output, "%s %s %zx %s\n",
+          dir == FROM_CLIENT? "client": "server",
+          prefix, remlen,
+          data);
+}
+
+
+/* return 0 on success */
+static int connack(FILE *dump, curl_socket_t fd)
+{
+  unsigned char packet[]={
+    MQTT_MSG_CONNACK, 0x02,
+    0x00, 0x00
+  };
+  ssize_t rc = swrite(fd, (char *)packet, sizeof(packet));
+  if(rc == sizeof(packet)) {
+    logmsg("WROTE %d bytes [CONACK]", rc);
+    loghex(packet, rc);
+    logprotocol(FROM_SERVER, "CONACK", 2, dump, packet, sizeof(packet));
+    return 0;
+  }
+  return 1;
+}
+
+/* return 0 on success */
+static int suback(FILE *dump, curl_socket_t fd, unsigned short packetid)
+{
+  unsigned char packet[]={
+    MQTT_MSG_SUBACK, 0x03,
+    0, 0, /* filled in below */
+    0x00
+  };
+  ssize_t rc;
+  packet[2] = (unsigned char)(packetid >> 8);
+  packet[3] = (unsigned char)(packetid & 0xff);
+
+  rc = swrite(fd, (char *)packet, sizeof(packet));
+  if(rc == sizeof(packet)) {
+    logmsg("WROTE %d bytes [SUBACK]", rc);
+    loghex(packet, rc);
+    logprotocol(FROM_SERVER, "SUBACK", 3, dump, packet, rc);
+    return 0;
+  }
+  return 1;
+}
+
+#ifdef QOS
+/* return 0 on success */
+static int puback(FILE *dump, curl_socket_t fd, unsigned short packetid)
+{
+  unsigned char packet[]={
+    MQTT_MSG_PUBACK, 0x00,
+    0, 0 /* filled in below */
+  };
+  ssize_t rc;
+  packet[2] = (unsigned char)(packetid >> 8);
+  packet[3] = (unsigned char)(packetid & 0xff);
+
+  rc = swrite(fd, (char *)packet, sizeof(packet));
+  if(rc == sizeof(packet)) {
+    logmsg("WROTE %d bytes [PUBACK]", rc);
+    loghex(packet, rc);
+    logprotocol(FROM_SERVER, dump, packet, rc);
+    return 0;
+  }
+  logmsg("Failed sending [PUBACK]");
+  return 1;
+}
+#endif
+
+/* return 0 on success */
+static int disconnect(FILE *dump, curl_socket_t fd)
+{
+  unsigned char packet[]={
+    MQTT_MSG_DISCONNECT, 0x00,
+  };
+  ssize_t rc = swrite(fd, (char *)packet, sizeof(packet));
+  if(rc == sizeof(packet)) {
+    logmsg("WROTE %d bytes [DISCONNECT]", rc);
+    loghex(packet, rc);
+    logprotocol(FROM_SERVER, "DISCONNECT", 0, dump, packet, rc);
+    return 0;
+  }
+  logmsg("Failed sending [DISCONNECT]");
+  return 1;
+}
+
+
+
+/*
+  do
+
+     encodedByte = X MOD 128
+
+     X = X DIV 128
+
+     // if there are more data to encode, set the top bit of this byte
+
+     if ( X > 0 )
+
+        encodedByte = encodedByte OR 128
+
+      endif
+
+    'output' encodedByte
+
+  while ( X > 0 )
+
+*/
+
+/* return number of bytes used */
+static int encode_length(size_t packetlen, char *remlength) /* 4 bytes */
+{
+  int bytes = 0;
+  unsigned char encode;
+
+  do {
+    encode = packetlen % 0x80;
+    packetlen /= 0x80;
+    if(packetlen)
+      encode |= 0x80;
+
+    remlength[bytes++] = encode;
+
+    if(bytes > 3) {
+      logmsg("too large packet!");
+      return 0;
+    }
+  } while(packetlen);
+
+  return bytes;
+}
+
+
+static size_t decode_length(unsigned char *buf,
+                            size_t buflen, size_t *lenbytes)
+{
+  size_t len = 0;
+  size_t mult = 1;
+  size_t i;
+  unsigned char encoded = 0x80;
+
+  for(i = 0; (i < buflen) && (encoded & 0x80); i++) {
+    encoded = buf[i];
+    len += (encoded & 0x7f) * mult;
+    mult *= 0x80;
+  }
+
+  if(lenbytes)
+    *lenbytes = i;
+
+  return len;
+}
+
+
+/* return 0 on success */
+static int publish(FILE *dump,
+                   curl_socket_t fd, unsigned short packetid,
+                   char *topic, char *payload, size_t payloadlen)
+{
+  size_t topiclen = strlen(topic);
+  unsigned char *packet;
+  size_t payloadindex;
+  ssize_t remaininglength = topiclen + 2 + payloadlen;
+  ssize_t packetlen;
+  ssize_t rc;
+  char rembuffer[4];
+  int encodedlen;
+
+  encodedlen = encode_length(remaininglength, rembuffer);
+
+  /* one packet type byte (possibly two more for packetid) */
+  packetlen = remaininglength + encodedlen + 1;
+  packet = malloc(packetlen);
+  if(!packet)
+    return 1;
+
+  packet[0] = MQTT_MSG_PUBLISH; /* TODO: set QoS? */
+  memcpy(&packet[1], rembuffer, encodedlen);
+
+  (void)packetid;
+  /* packet_id if QoS is set */
+
+  packet[1 + encodedlen] = (unsigned char)(topiclen >> 8);
+  packet[2 + encodedlen] = (unsigned char)(topiclen & 0xff);
+  memcpy(&packet[3 + encodedlen], topic, topiclen);
+
+  payloadindex = 3 + topiclen + encodedlen;
+  memcpy(&packet[payloadindex], payload, payloadlen);
+
+  rc = swrite(fd, (char *)packet, packetlen);
+  if(rc == packetlen) {
+    logmsg("WROTE %d bytes [PUBLISH]", rc);
+    loghex(packet, rc);
+    logprotocol(FROM_SERVER, "PUBLISH", remaininglength, dump, packet, rc);
+    return 0;
+  }
+  return 1;
+}
+
+#define MAX_TOPIC_LENGTH 65535
+#define MAX_CLIENT_ID_LENGTH 32
+
+static char topic[MAX_TOPIC_LENGTH + 1];
+
+static int fixedheader(curl_socket_t fd,
+                       unsigned char *bytep,
+                       size_t *remaining_lengthp,
+                       size_t *remaining_length_bytesp)
+{
+  /* get the fixed header */
+  unsigned char buffer[10];
+
+  /* get the first two bytes */
+  ssize_t rc = sread(fd, (char *)buffer, 2);
+  int i;
+  if(rc < 2) {
+    logmsg("READ %d bytes [SHORT!]", rc);
+    return 1; /* fail */
+  }
+  logmsg("READ %d bytes", rc);
+  loghex(buffer, rc);
+  *bytep = buffer[0];
+
+  /* if the length byte has the top bit set, get the next one too */
+  i = 1;
+  while(buffer[i] & 0x80) {
+    i++;
+    rc = sread(fd, (char *)&buffer[i], 1);
+    if(rc != 1) {
+      logmsg("Remaining Length broken");
+      return 1;
+    }
+  }
+  *remaining_lengthp = decode_length(&buffer[1], i, remaining_length_bytesp);
+  logmsg("Remaining Length: %ld [%d bytes]", (long) *remaining_lengthp,
+         *remaining_length_bytesp);
+  return 0;
+}
+
+static curl_socket_t mqttit(curl_socket_t fd)
+{
+  unsigned char buffer[10*1024];
+  ssize_t rc;
+  unsigned char byte;
+  unsigned short packet_id;
+  size_t payload_len;
+  unsigned int topic_len;
+  size_t remaining_length = 0;
+  size_t bytes = 0; /* remaining length field size in bytes */
+  char client_id[MAX_CLIENT_ID_LENGTH];
+  char *filename;
+  long testno;
+
+  static const char protocol[7] = {
+    0x00, 0x04,       /* protocol length */
+    'M','Q','T','T',  /* protocol name */
+    0x04              /* protocol level */
+  };
+  FILE *dump = fopen(REQUEST_DUMP, "ab");
+  if(!dump)
+    goto end;
+
+  getconfig();
+
+  do {
+    /* get the fixed header */
+    rc = fixedheader(fd, &byte, &remaining_length, &bytes);
+    if(rc)
+      break;
+    if(remaining_length) {
+      rc = sread(fd, (char *)buffer, remaining_length);
+      if(rc > 0) {
+        logmsg("READ %d bytes", rc);
+        loghex(buffer, rc);
+      }
+    }
+
+    if(byte == MQTT_MSG_CONNECT) {
+      logprotocol(FROM_CLIENT, "CONNECT", remaining_length,
+                  dump, buffer, rc);
+
+      if(memcmp(protocol, buffer, sizeof(protocol))) {
+        logmsg("Protocol preamble mismatch");
+        goto end;
+      }
+      /* ignore the connect flag byte and two keepalive bytes */
+
+      payload_len = (buffer[10] << 8) | buffer[11];
+      if((ssize_t)payload_len != (rc - 12)) {
+        logmsg("Payload length mismatch, expected %x got %x",
+               rc - 12, payload_len);
+        goto end;
+      }
+      else if((payload_len + 1) > MAX_CLIENT_ID_LENGTH) {
+        logmsg("Too large client id");
+        goto end;
+      }
+      memcpy(client_id, &buffer[14], payload_len);
+      client_id[payload_len] = 0;
+
+      logmsg("MQTT client connect accepted: %s", client_id);
+
+      /* The first packet sent from the Server to the Client MUST be a
+         CONNACK Packet */
+
+      if(connack(dump, fd)) {
+        logmsg("failed sending CONNACK");
+        goto end;
+      }
+    }
+    else if(byte == MQTT_MSG_SUBSCRIBE) {
+      char *testnop;
+
+      logprotocol(FROM_CLIENT, "SUBSCRIBE", remaining_length,
+                  dump, buffer, rc);
+      logmsg("Incoming SUBSCRIBE");
+
+      if(rc < 6) {
+        logmsg("Too small SUBSCRIBE");
+        goto end;
+      }
+
+      /* two bytes packet id */
+      packet_id = (unsigned short)((buffer[0] << 8) | buffer[1]);
+
+      /* two bytes topic length */
+      topic_len = (buffer[2] << 8) | buffer[3];
+      if(topic_len != (remaining_length - 5)) {
+        logmsg("Wrong topic length, got %d expected %d",
+               topic_len, remaining_length - 5);
+        goto end;
+      }
+      memcpy(topic, &buffer[4], topic_len);
+      topic[topic_len] = 0;
+
+      /* there's a QoS byte (two bits) after the topic */
+
+      logmsg("SUBSCRIBE to '%s' [%d]", topic, packet_id);
+      if(suback(dump, fd, packet_id)) {
+        logmsg("failed sending SUBACK");
+        goto end;
+      }
+      testnop = strrchr(topic, '/');
+      if(!testnop)
+        testnop = topic;
+      else
+        testnop++; /* pass the slash */
+      testno = strtol(testnop, NULL, 10);
+      if(testno) {
+        FILE *stream;
+        int error;
+        char *data;
+        size_t datalen;
+        logmsg("Found test number %ld", testno);
+        filename = test2file(testno);
+        stream = fopen(filename, "rb");
+        error = getpart(&data, &datalen, "reply", "data", stream);
+        if(!error)
+          publish(dump, fd, packet_id, topic, data, datalen);
+      }
+      else {
+        char *def = (char *)"this is random payload yes yes it is";
+        publish(dump, fd, packet_id, topic, def, strlen(def));
+      }
+      disconnect(dump, fd);
+    }
+    else if((byte & 0xf0) == (MQTT_MSG_PUBLISH & 0xf0)) {
+      size_t topiclen;
+
+      logmsg("Incoming PUBLISH");
+      logprotocol(FROM_CLIENT, "PUBLISH", remaining_length,
+                  dump, buffer, rc);
+
+      topiclen = (buffer[1 + bytes] << 8) | buffer[2 + bytes];
+      logmsg("Got %d bytes topic", topiclen);
+      /* TODO: verify topiclen */
+
+#ifdef QOS
+      /* TODO: handle packetid if there is one. Send puback if QoS > 0 */
+      puback(dump, fd, 0);
+#endif
+      /* expect a disconnect here */
+      /* get the request */
+      rc = sread(fd, (char *)&buffer[0], 2);
+
+      logmsg("READ %d bytes [DISCONNECT]", rc);
+      loghex(buffer, rc);
+      logprotocol(FROM_CLIENT, "DISCONNECT", 0, dump, buffer, rc);
+      goto end;
+    }
+    else {
+      /* not supported (yet) */
+      goto end;
+    }
+  } while(1);
+
+  end:
+  fclose(dump);
+  return CURL_SOCKET_BAD;
+}
+
+/*
+  sockfdp is a pointer to an established stream or CURL_SOCKET_BAD
+
+  if sockfd is CURL_SOCKET_BAD, listendfd is a listening socket we must
+  accept()
+*/
+static bool incoming(curl_socket_t listenfd)
+{
+  fd_set fds_read;
+  fd_set fds_write;
+  fd_set fds_err;
+  int clients = 0; /* connected clients */
+
+  if(got_exit_signal) {
+    logmsg("signalled to die, exiting...");
+    return FALSE;
+  }
+
+#ifdef HAVE_GETPPID
+  /* As a last resort, quit if socks5 process becomes orphan. */
+  if(getppid() <= 1) {
+    logmsg("process becomes orphan, exiting");
+    return FALSE;
+  }
+#endif
+
+  do {
+    ssize_t rc;
+    int error = 0;
+    curl_socket_t sockfd = listenfd;
+    int maxfd = (int)sockfd;
+
+    FD_ZERO(&fds_read);
+    FD_ZERO(&fds_write);
+    FD_ZERO(&fds_err);
+
+    /* there's always a socket to wait for */
+    FD_SET(sockfd, &fds_read);
+
+    do {
+      /* select() blocking behavior call on blocking descriptors please */
+      rc = select(maxfd + 1, &fds_read, &fds_write, &fds_err, NULL);
+      if(got_exit_signal) {
+        logmsg("signalled to die, exiting...");
+        return FALSE;
+      }
+    } while((rc == -1) && ((error = errno) == EINTR));
+
+    if(rc < 0) {
+      logmsg("select() failed with error: (%d) %s",
+             error, strerror(error));
+      return FALSE;
+    }
+
+    if(FD_ISSET(sockfd, &fds_read)) {
+      curl_socket_t newfd = accept(sockfd, NULL, NULL);
+      if(CURL_SOCKET_BAD == newfd) {
+        error = SOCKERRNO;
+        logmsg("accept(%d, NULL, NULL) failed with error: (%d) %s",
+               sockfd, error, strerror(error));
+      }
+      else {
+        logmsg("====> Client connect, fd %d. Read config from %s",
+               newfd, configfile);
+        set_advisor_read_lock(SERVERLOGS_LOCK);
+        (void)mqttit(newfd); /* until done */
+        clear_advisor_read_lock(SERVERLOGS_LOCK);
+
+        logmsg("====> Client disconnect");
+        sclose(newfd);
+      }
+    }
+  } while(clients);
+
+  return TRUE;
+}
+
+static curl_socket_t sockdaemon(curl_socket_t sock,
+                                unsigned short *listenport)
+{
+  /* passive daemon style */
+  srvr_sockaddr_union_t listener;
+  int flag;
+  int rc;
+  int totdelay = 0;
+  int maxretr = 10;
+  int delay = 20;
+  int attempt = 0;
+  int error = 0;
+
+  do {
+    attempt++;
+    flag = 1;
+    rc = setsockopt(sock, SOL_SOCKET, SO_REUSEADDR,
+         (void *)&flag, sizeof(flag));
+    if(rc) {
+      error = SOCKERRNO;
+      logmsg("setsockopt(SO_REUSEADDR) failed with error: (%d) %s",
+             error, strerror(error));
+      if(maxretr) {
+        rc = wait_ms(delay);
+        if(rc) {
+          /* should not happen */
+          error = errno;
+          logmsg("wait_ms() failed with error: (%d) %s",
+                 error, strerror(error));
+          sclose(sock);
+          return CURL_SOCKET_BAD;
+        }
+        if(got_exit_signal) {
+          logmsg("signalled to die, exiting...");
+          sclose(sock);
+          return CURL_SOCKET_BAD;
+        }
+        totdelay += delay;
+        delay *= 2; /* double the sleep for next attempt */
+      }
+    }
+  } while(rc && maxretr--);
+
+  if(rc) {
+    logmsg("setsockopt(SO_REUSEADDR) failed %d times in %d ms. Error: (%d) %s",
+           attempt, totdelay, error, strerror(error));
+    logmsg("Continuing anyway...");
+  }
+
+  /* When the specified listener port is zero, it is actually a
+     request to let the system choose a non-zero available port. */
+
+#ifdef ENABLE_IPV6
+  if(!use_ipv6) {
+#endif
+    memset(&listener.sa4, 0, sizeof(listener.sa4));
+    listener.sa4.sin_family = AF_INET;
+    listener.sa4.sin_addr.s_addr = INADDR_ANY;
+    listener.sa4.sin_port = htons(*listenport);
+    rc = bind(sock, &listener.sa, sizeof(listener.sa4));
+#ifdef ENABLE_IPV6
+  }
+  else {
+    memset(&listener.sa6, 0, sizeof(listener.sa6));
+    listener.sa6.sin6_family = AF_INET6;
+    listener.sa6.sin6_addr = in6addr_any;
+    listener.sa6.sin6_port = htons(*listenport);
+    rc = bind(sock, &listener.sa, sizeof(listener.sa6));
+  }
+#endif /* ENABLE_IPV6 */
+  if(rc) {
+    error = SOCKERRNO;
+    logmsg("Error binding socket on port %hu: (%d) %s",
+           *listenport, error, strerror(error));
+    sclose(sock);
+    return CURL_SOCKET_BAD;
+  }
+
+  if(!*listenport) {
+    /* The system was supposed to choose a port number, figure out which
+       port we actually got and update the listener port value with it. */
+    curl_socklen_t la_size;
+    srvr_sockaddr_union_t localaddr;
+#ifdef ENABLE_IPV6
+    if(!use_ipv6)
+#endif
+      la_size = sizeof(localaddr.sa4);
+#ifdef ENABLE_IPV6
+    else
+      la_size = sizeof(localaddr.sa6);
+#endif
+    memset(&localaddr.sa, 0, (size_t)la_size);
+    if(getsockname(sock, &localaddr.sa, &la_size) < 0) {
+      error = SOCKERRNO;
+      logmsg("getsockname() failed with error: (%d) %s",
+             error, strerror(error));
+      sclose(sock);
+      return CURL_SOCKET_BAD;
+    }
+    switch(localaddr.sa.sa_family) {
+    case AF_INET:
+      *listenport = ntohs(localaddr.sa4.sin_port);
+      break;
+#ifdef ENABLE_IPV6
+    case AF_INET6:
+      *listenport = ntohs(localaddr.sa6.sin6_port);
+      break;
+#endif
+    default:
+      break;
+    }
+    if(!*listenport) {
+      /* Real failure, listener port shall not be zero beyond this point. */
+      logmsg("Apparently getsockname() succeeded, with listener port zero.");
+      logmsg("A valid reason for this failure is a binary built without");
+      logmsg("proper network library linkage. This might not be the only");
+      logmsg("reason, but double check it before anything else.");
+      sclose(sock);
+      return CURL_SOCKET_BAD;
+    }
+  }
+
+  /* start accepting connections */
+  rc = listen(sock, 5);
+  if(0 != rc) {
+    error = SOCKERRNO;
+    logmsg("listen(%d, 5) failed with error: (%d) %s",
+           sock, error, strerror(error));
+    sclose(sock);
+    return CURL_SOCKET_BAD;
+  }
+
+  return sock;
+}
+
+
+int main(int argc, char *argv[])
+{
+  curl_socket_t sock = CURL_SOCKET_BAD;
+  curl_socket_t msgsock = CURL_SOCKET_BAD;
+  int wrotepidfile = 0;
+  int wroteportfile = 0;
+  const char *pidname = ".mqttd.pid";
+  const char *portname = ".mqttd.port";
+  bool juggle_again;
+  int error;
+  int arg = 1;
+
+  while(argc>arg) {
+    if(!strcmp("--version", argv[arg])) {
+      printf("mqttd IPv4%s\n",
+#ifdef ENABLE_IPV6
+             "/IPv6"
+#else
+             ""
+#endif
+             );
+      return 0;
+    }
+    else if(!strcmp("--pidfile", argv[arg])) {
+      arg++;
+      if(argc>arg)
+        pidname = argv[arg++];
+    }
+    else if(!strcmp("--portfile", argv[arg])) {
+      arg++;
+      if(argc>arg)
+        portname = argv[arg++];
+    }
+    else if(!strcmp("--config", argv[arg])) {
+      arg++;
+      if(argc>arg)
+        configfile = argv[arg++];
+    }
+    else if(!strcmp("--logfile", argv[arg])) {
+      arg++;
+      if(argc>arg)
+        serverlogfile = argv[arg++];
+    }
+    else if(!strcmp("--ipv6", argv[arg])) {
+#ifdef ENABLE_IPV6
+      ipv_inuse = "IPv6";
+      use_ipv6 = TRUE;
+#endif
+      arg++;
+    }
+    else if(!strcmp("--ipv4", argv[arg])) {
+      /* for completeness, we support this option as well */
+#ifdef ENABLE_IPV6
+      ipv_inuse = "IPv4";
+      use_ipv6 = FALSE;
+#endif
+      arg++;
+    }
+    else if(!strcmp("--port", argv[arg])) {
+      arg++;
+      if(argc>arg) {
+        char *endptr;
+        unsigned long ulnum = strtoul(argv[arg], &endptr, 10);
+        if((endptr != argv[arg] + strlen(argv[arg])) ||
+           ((ulnum != 0UL) && ((ulnum < 1025UL) || (ulnum > 65535UL)))) {
+          fprintf(stderr, "mqttd: invalid --port argument (%s)\n",
+                  argv[arg]);
+          return 0;
+        }
+        port = curlx_ultous(ulnum);
+        arg++;
+      }
+    }
+    else {
+      puts("Usage: mqttd [option]\n"
+           " --config [file]\n"
+           " --version\n"
+           " --logfile [file]\n"
+           " --pidfile [file]\n"
+           " --ipv4\n"
+           " --ipv6\n"
+           " --port [port]\n");
+      return 0;
+    }
+  }
+
+#ifdef WIN32
+  win32_init();
+  atexit(win32_cleanup);
+
+  setmode(fileno(stdin), O_BINARY);
+  setmode(fileno(stdout), O_BINARY);
+  setmode(fileno(stderr), O_BINARY);
+#endif
+
+  install_signal_handlers(FALSE);
+
+#ifdef ENABLE_IPV6
+  if(!use_ipv6)
+#endif
+    sock = socket(AF_INET, SOCK_STREAM, 0);
+#ifdef ENABLE_IPV6
+  else
+    sock = socket(AF_INET6, SOCK_STREAM, 0);
+#endif
+
+  if(CURL_SOCKET_BAD == sock) {
+    error = SOCKERRNO;
+    logmsg("Error creating socket: (%d) %s",
+           error, strerror(error));
+    goto mqttd_cleanup;
+  }
+
+  {
+    /* passive daemon style */
+    sock = sockdaemon(sock, &port);
+    if(CURL_SOCKET_BAD == sock) {
+      goto mqttd_cleanup;
+    }
+    msgsock = CURL_SOCKET_BAD; /* no stream socket yet */
+  }
+
+  logmsg("Running %s version", ipv_inuse);
+  logmsg("Listening on port %hu", port);
+
+  wrotepidfile = write_pidfile(pidname);
+  if(!wrotepidfile) {
+    goto mqttd_cleanup;
+  }
+
+  wroteportfile = write_portfile(portname, (int)port);
+  if(!wroteportfile) {
+    goto mqttd_cleanup;
+  }
+
+  do {
+    juggle_again = incoming(sock);
+  } while(juggle_again);
+
+mqttd_cleanup:
+
+  if((msgsock != sock) && (msgsock != CURL_SOCKET_BAD))
+    sclose(msgsock);
+
+  if(sock != CURL_SOCKET_BAD)
+    sclose(sock);
+
+  if(wrotepidfile)
+    unlink(pidname);
+
+  restore_signal_handlers(FALSE);
+
+  if(got_exit_signal) {
+    logmsg("============> mqttd exits with signal (%d)", exit_signal);
+    /*
+     * To properly set the return status of the process we
+     * must raise the same signal SIGINT or SIGTERM that we
+     * caught and let the old handler take care of it.
+     */
+    raise(exit_signal);
+  }
+
+  logmsg("============> mqttd quits");
+  return 0;
+}
diff --git a/tests/server/util.c b/tests/server/util.c
index 65d491c0b..169ca5bcb 100644
--- a/tests/server/util.c
+++ b/tests/server/util.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -284,6 +284,20 @@ int write_pidfile(const char *filename)
   return 1; /* success */
 }
 
+/* store the used port number in a file */
+int write_portfile(const char *filename, int port)
+{
+  FILE *portfile = fopen(filename, "wb");
+  if(!portfile) {
+    logmsg("Couldn't write port file: %s %s", filename, strerror(errno));
+    return 0; /* fail */
+  }
+  fprintf(portfile, "%d\n", port);
+  fclose(portfile);
+  logmsg("Wrote port %d to %s", port, filename);
+  return 1; /* success */
+}
+
 void set_advisor_read_lock(const char *filename)
 {
   FILE *lockfile;
diff --git a/tests/server/util.h b/tests/server/util.h
index 0446b6a84..9c3fb9f32 100644
--- a/tests/server/util.h
+++ b/tests/server/util.h
@@ -55,15 +55,11 @@ void win32_cleanup(void);
 
 /* returns the path name to the test case file */
 char *test2file(long testno);
-
 int wait_ms(int timeout_ms);
-
 int write_pidfile(const char *filename);
-
+int write_portfile(const char *filename, int port);
 void set_advisor_read_lock(const char *filename);
-
 void clear_advisor_read_lock(const char *filename);
-
 int strncasecompare(const char *first, const char *second, size_t max);
 
 /* global variable which if set indicates that the program should finish */