查找订阅系统主题短时间自动断开原因，该时间与sys_interval有关，若该时间

内没有该主题的消息发布，则当server读到数据长度为0时，自动断开。（此处
处理可优化）若有消息发布，则可一直保持连接

lib/net_mosq.c

@@ -855,7 +855,7 @@ int _mosquitto_packet_read(struct mosquitto *mosq)
  if(!(mosq->bridge) && mosq->state == mosq_cs_new && (byte&0xF0) != CONNECT) return MOSQ_ERR_PROTOCOL;
 #endif
  }else{
- if(read_length == 0) return MOSQ_ERR_CONN_LOST; /* EOF */
+ if(read_length == 0) return MOSQ_ERR_CONN_LOST; /* EOF*/
 #ifdef WIN32
  errno = WSAGetLastError();
 #endif
@@ -887,7 +887,7 @@ int _mosquitto_packet_read(struct mosquitto *mosq)
  mosq->in_packet.remaining_length += (byte & 127) * mosq->in_packet.remaining_mult;
  mosq->in_packet.remaining_mult *= 128;
  }else{
- if(read_length == 0) return MOSQ_ERR_CONN_LOST; /* EOF */
+ if(read_length == 0) return MOSQ_ERR_CONN_LOST; /* EOF  MOSQ_ERR_CONN_LOST的值为7，系统自动断开的情况都是从这里开始*/
 #ifdef WIN32
  errno = WSAGetLastError();
 #endif

src/conf.c

@@ -165,7 +165,7 @@ static void _config_init_reload(struct mqtt3_config *config)
  config->retry_interval = 20;
  config->store_clean_interval = 10;
  //config->sys_interval = 900;
- config->sys_interval = 10;
+ config->sys_interval = 40;
  config->upgrade_outgoing_qos = false;
  if(config->auth_options){
  for(i=0; i<config->auth_option_count; i++){

src/loop.c

@@ -337,6 +337,7 @@ static void loop_handle_errors(struct mosquitto_db *db, struct pollfd *pollfds)
 static void loop_handle_reads_writes(struct mosquitto_db *db, struct pollfd *pollfds)
 {
  int i;
+ int rc;
 
  for(i=0; i<db->context_count; i++){
  if(db->contexts[i] && db->contexts[i]->sock != INVALID_SOCKET){//判断是否有数据需要写
@@ -363,9 +364,9 @@ static void loop_handle_reads_writes(struct mosquitto_db *db, struct pollfd *pol
 #else
  if(pollfds[db->contexts[i]->pollfd_index].revents & POLLIN){
 #endif
- if(_mosquitto_packet_read(db, db->contexts[i])){
+ if(rc = _mosquitto_packet_read(db, db->contexts[i])){
  do_disconnect(db, i);
- printf("read error,disconnect!\n");
+ printf("read error,disconnect!rc=%d\n", rc);
  }
  printf("read data!\n");
  }