使用select io复用实现超时设置

在linux的socket编程中，经常会遇到超时设置的问题，例如请求方如果在Ks内不发送数据则服务器要断开连接停止服务。这里我使用select的io复用实现超时5s设置，具体代码片段如下：

fd_set fs;

timeval tv;

tv.tv_sec = 5;

tv.tv_usec = 0;

FD_ZERO(&fs);

FD_SET(socket_fd,&fs);

int ret = select(socket_fd+1,&fs,NULL,NULL,&tv);

if(ret == -1){

  fprintf(stderr, "socket_job:run:error.\n");

}else if(ret == 0){

 fprintf(stderr, "socket_job:run:time out.\n");

}else{

  if(FD_ISSET(socket_fd,&fs)){

  int length = 1024*1024;

  char* buffer = new char[length];

  memset(buffer,0,sizeof(char)*length);

  int n = recv(socket_fd,buffer,sizeof(char)*length,0);

  if(n > 0){

    //deal msg

    buffer[length] = '\0';

    search_collector* searcher = new search_collector();

    string result("");

    searcher->search(buffer,10,result);

    //send result,result must be end with \n

    int result_length = strlen(result.c_str());

    ret = send(socket_fd,result.c_str(),result_length,0);

    int all_send = 0;

    while(ret > 0 && ret < result_length){

       result_length -= ret;

       all_send += ret;

       ret = send(socket_fd,result.c_str()+all_send,result_length,0);

    }

 }

 delete[] buffer;

} }