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This article will explain in detail how to analyze UDP protocol, the content of the article is of high quality, so Xiaobian shares it with you as a reference, I hope you have a certain understanding of relevant knowledge after reading this article.

1. Socket

Socket: IP address + port number. In TCP/IP, it uniquely identifies a process in network communication. Sockets are used to describe one-to-one relationships between network connections.

TCP/IP protocol stipulates that network data flow should adopt big endian byte order, that is,(memory) low address high byte (data).

UDP_SOCKET

UDP Protocol----User Datagram Protocol (connection-oriented)--- SOCK_DDRAM

h represents host,n represents network,l represents 32-bit long integer,s represents 16-bit short integer.

IPv4 address format is defined in netinet/in.h,IPv4 address: sockaddr_in structure, including 16-bit port number and 32-bit IP address

struct sockaddr_in { uint8_t sin_len; sa_family_t sin_family; in_port_t sin_port; struct in_addr sin_addr; char sin_zero[8];};

UDP socket instance:

//udp_server.c

#include #include#include#include#include#include#include#include#includevoid usage(const char *proc){ printf("%s:[ip][port]\n",proc);}int main(int argc,char *argv[]){ if(argc != 3) { usage(argv[0]); return 1; } char *_ip=argv[1]; int _port=atoi(argv[2]); int sock=socket(AF_INET,SOCK_DGRAM,0); if(sock

< 0) { perror("socket"); exit(1); } struct sockaddr_in local; local.sin_family=AF_INET; local.sin_port=htons(_port); local.sin_addr.s_addr=inet_addr(_ip); if(bind(sock,(struct sockaddr*)&local,sizeof(local)) < 0) { perror("bind"); exit(2); } int done=0; char buf[1024]; struct sockaddr_in client; socklen_t len=sizeof(client); while(!done) { ssize_t _size=recvfrom(sock,buf,sizeof(buf)-1,0,(struct sockaddr*)&client,&len); if(_size >

0) { buf[_size]='\0'; printf("[%s : %d]: %s\n",inet_ntoa(client.sin_addr),ntohs(client.sin_port),buf); } else if(_size == 0) { printf("client close...\ n"); } else {} } return 0;}

//udp_client.c

#include #include#include#include#include#include#include#include#includevoid usage(const char *proc){ printf("%s:[ip][port]\n",proc);}int main(int argc,char *argv[]){ if(argc != 3) { usage(argv[0]); return 1; } char *_ip=argv[1]; int _port=atoi(argv[2]); int sock=socket(AF_INET,SOCK_DGRAM,0); if(sock

< 0) { perror("socket"); exit(1); } struct sockaddr_in local; local.sin_family=AF_INET; local.sin_port=htons(_port); local.sin_addr.s_addr=inet_addr(_ip); if(bind(sock,(struct sockaddr*)&local,sizeof(local)) < 0) { perror("bind"); exit(2); } int done=0; char buf[1024]; struct sockaddr_in client; socklen_t len=sizeof(client); while(!done) { ssize_t _size=recvfrom(sock,buf,sizeof(buf)-1,0,(struct sockaddr*)&client,&len); if(_size >

0) { buf[_size]='\0'; printf("[%s : %d]: %s\n",inet_ntoa(client.sin_addr),ntohs(client.sin_port),buf); } else if(_size == 0) { printf("client close...\ n"); } else {} } return 0;}

Run Results:

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