优化小包传输实时性:解析NODELAY对TCP/IP延时的影响

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资源摘要信息:"本文档主要探讨了在TCP/IP协议中,如何通过设置NODELAY选项来减少小数据包的传输延迟,提高小数据包的实时性。" 在计算机网络中,TCP/IP协议是最常用的通信协议。在进行网络通信时,数据会被划分为一个个的数据包进行传输。然而,由于网络环境的复杂性,数据包在传输过程中可能会出现延迟,特别是在数据量较小的情况下,这种延迟更为明显。这就是我们常说的小包延迟问题。 为了减少这种延迟,我们可以采用一种称为NODELAY的技术。NODELAY是一种TCP/IP协议的参数设置,它的作用是告诉TCP协议,不要将数据包合并再发送,而是尽可能快地发送每个数据包。这样,就可以减少数据包在网络中的停留时间,从而减少延迟。 在TCP/IP协议中,数据包的发送有两种模式:一种是Nagle算法,一种是NODELAY模式。Nagle算法会尽量减少网络中的小数据包数量,它会将小的数据包合并后再发送,以减少网络拥塞。然而,这也会导致数据包的延迟。而NODELAY模式则恰恰相反,它会尽可能快地发送每个数据包,以减少延迟。 然而,使用NODELAY也会带来一些问题。由于每个数据包都是立即发送,这可能会导致网络拥塞,进而影响数据传输的效率。因此,在实际应用中,我们需要根据实际情况来选择是否使用NODELAY。 在实际的网络编程中,我们可以使用setsockopt函数来设置NODELAY选项。例如,在C语言中,我们可以使用以下代码来设置NODELAY: int nodelay = 1; setsockopt(sockfd, IPPROTO_TCP, TCP_NODELAY, (const void *)&nodelay , sizeof(nodelay)); 以上代码中,sockfd是套接字的文件描述符,IPPROTO_TCP表示我们要设置的选项属于TCP协议,TCP_NODELAY是我们要设置的选项名称,nodelay是我们要设置的选项值,它的值为1表示启用NODELAY模式。 总的来说,NODELAY是一种有效的减少小数据包延迟的技术,但在使用时也需要考虑到它可能带来的网络拥塞问题。我们需要根据实际的网络环境和需求,来决定是否启用NODELAY模式。

[ 3%] Generating dynamic reconfigure files from cfg/Params_PID.cfg: /home/ubuntu/new_workspace/devel/include/simple_follower/Params_PIDConfig.h /home/ubuntu/new_workspace/devel/lib/python2.7/dist-packages/simple_follower/cfg/Params_PIDConfig.py Generating reconfiguration files for Params_PID in simple_follower Wrote header file in /home/ubuntu/new_workspace/devel/include/simple_follower/Params_PIDConfig.h In file included from /home/ubuntu/new_workspace/src/lsx10/lslidar_x10_driver/src/input.cc:18:0: /home/ubuntu/new_workspace/src/lsx10/lslidar_x10_driver/include/lslidar_x10_driver/input.h:35:10: fatal error: lslidar_x10_msgs/LslidarX10Packet.h: No such file or directory #include <lslidar_x10_msgs/LslidarX10Packet.h> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ compilation terminated. lsx10/lslidar_x10_driver/CMakeFiles/lslidar_input_x10.dir/build.make:62: recipe for target 'lsx10/lslidar_x10_driver/CMakeFiles/lslidar_input_x10.dir/src/input.cc.o' failed make[2]: *** [lsx10/lslidar_x10_driver/CMakeFiles/lslidar_input_x10.dir/src/input.cc.o] Error 1 CMakeFiles/Makefile2:10548: recipe for target 'lsx10/lslidar_x10_driver/CMakeFiles/lslidar_input_x10.dir/all' failed make[1]: *** [lsx10/lslidar_x10_driver/CMakeFiles/lslidar_input_x10.dir/all] Error 2 make[1]: *** Waiting for unfinished jobs.... Generating reconfiguration files for params in rplidar_ros Wrote header file in /home/ubuntu/new_workspace/devel/include/rplidar_ros/paramsConfig.h [ 3%] Built target simple_follower_gencfg [ 3%] Built target rplidar_ros_gencfg [ 3%] Linking CXX executable /home/ubuntu/new_workspace/devel/lib/rplidar_ros/rplidarNodeClient [ 3%] Built target rplidarNodeClient Makefile:140: recipe for target 'all' failed make: *** [all] Error 2 Invoking "make -j4 -l4" failed

2023-05-26 上传

[ 12%] Building CXX object usb_cam/CMakeFiles/v4l_driver.dir/src/camera_driver.cpp.o /root/catkin_uc/src/usb_cam/src/camera_driver.cpp: In destructor ‘virtual usb_cam::AbstractV4LUSBCam::~AbstractV4LUSBCam()’: /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:239:5: error: ‘av_packet_free’ was not declared in this scope av_packet_free(&avpkt); ^~~~~~~~~~~~~~ /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:239:5: note: suggested alternative: ‘av_packet_ref’ av_packet_free(&avpkt); ^~~~~~~~~~~~~~ av_packet_ref /root/catkin_uc/src/usb_cam/src/camera_driver.cpp: In static member function ‘static bool usb_cam::AbstractV4LUSBCam::init_decoder()’: /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:379:13: error: ‘av_packet_alloc’ was not declared in this scope avpkt = av_packet_alloc(); ^~~~~~~~~~~~~~~ /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:379:13: note: suggested alternative: ‘av_image_alloc’ avpkt = av_packet_alloc(); ^~~~~~~~~~~~~~~ av_image_alloc /root/catkin_uc/src/usb_cam/src/camera_driver.cpp: In static member function ‘static bool usb_cam::AbstractV4LUSBCam::decode_ffmpeg(const void*, int, usb_cam::camera_image_t*)’: /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:779:8: error: ‘avcodec_send_packet’ was not declared in this scope if(avcodec_send_packet(avcodec_context, avpkt) < 0) ^~~~~~~~~~~~~~~~~~~ /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:779:8: note: suggested alternative: ‘av_append_packet’ if(avcodec_send_packet(avcodec_context, avpkt) < 0) ^~~~~~~~~~~~~~~~~~~ av_append_packet /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:792:9: error: ‘avcodec_receive_frame’ was not declared in this scope if (avcodec_receive_frame(avcodec_context, avframe_camera) < 0) ^~~~~~~~~~~~~~~~~~~~~ /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:792:9: note: suggested alternative: ‘avcodec_free_frame’ if (avcodec_receive_frame(avcodec_context, avframe_camera) < 0) ^~~~~~~~~~~~~~~~~~~~~ avcodec_free_frame usb_cam/CMakeFiles/v4l_driver.dir/build.make:110: recipe for target 'usb_cam/CMakeFiles/v4l_driver.dir/src/camera_driver.cpp.o' failed make[2]: *** [usb_cam/CMakeFiles/v4l_driver.dir/src/camera_driver.cpp.o] Error 1 CMakeFiles/Makefile2:656: recipe for target 'usb_cam/CMakeFiles/v4l_driver.dir/all' failed make[1]: *** [usb_cam/CMakeFiles/v4l_driver.dir/all] Error 2 Makefile:140: recipe for target 'all' failed make: *** [all] Error 2 Invoking "make -j4 -l4" failed

2023-07-16 上传

/root/catkin_uc/src/usb_cam/src/camera_driver.cpp: In destructor ‘virtual usb_cam::AbstractV4LUSBCam::~AbstractV4LUSBCam()’: /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:237:5: error: ‘av_packet_free’ was not declared in this scope av_packet_free(&avpkt); ^~~~~~~~~~~~~~ /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:237:5: note: suggested alternative: ‘av_packet_ref’ av_packet_free(&avpkt); ^~~~~~~~~~~~~~ av_packet_ref /root/catkin_uc/src/usb_cam/src/camera_driver.cpp: In static member function ‘static bool usb_cam::AbstractV4LUSBCam::init_decoder()’: /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:377:13: error: ‘av_packet_alloc’ was not declared in this scope avpkt = av_packet_alloc(); ^~~~~~~~~~~~~~~ /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:377:13: note: suggested alternative: ‘av_image_alloc’ avpkt = av_packet_alloc(); ^~~~~~~~~~~~~~~ av_image_alloc /root/catkin_uc/src/usb_cam/src/camera_driver.cpp: In static member function ‘static bool usb_cam::AbstractV4LUSBCam::decode_ffmpeg(const void*, int, usb_cam::camera_image_t*)’: /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:777:8: error: ‘avcodec_send_packet’ was not declared in this scope if(avcodec_send_packet(avcodec_context, avpkt) < 0) ^~~~~~~~~~~~~~~~~~~ /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:777:8: note: suggested alternative: ‘av_append_packet’ if(avcodec_send_packet(avcodec_context, avpkt) < 0) ^~~~~~~~~~~~~~~~~~~ av_append_packet /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:790:9: error: ‘avcodec_receive_frame’ was not declared in this scope if (avcodec_receive_frame(avcodec_context, avframe_camera) < 0) ^~~~~~~~~~~~~~~~~~~~~ /root/catkin_uc/src/usb_cam/src/camera_driver.cpp:790:9: note: suggested alternative: ‘avcodec_free_frame’ if (avcodec_receive_frame(avcodec_context, avframe_camera) < 0) ^~~~~~~~~~~~~~~~~~~~~ avcodec_free_frame usb_cam/CMakeFiles/v4l_driver.dir/build.make:110: recipe for target 'usb_cam/CMakeFiles/v4l_driver.dir/src/camera_driver.cpp.o' failed make[2]: *** [usb_cam/CMakeFiles/v4l_driver.dir/src/camera_driver.cpp.o] Error 1 CMakeFiles/Makefile2:656: recipe for target 'usb_cam/CMakeFiles/v4l_driver.dir/all' failed make[1]: *** [usb_cam/CMakeFiles/v4l_driver.dir/all] Error 2 Makefile:140: recipe for target 'all' failed make: *** [all] Error 2 Invoking "make -j4 -l4" failed

2023-07-16 上传