UDP calls the Connect function

Conclusion:
UDP can call the Connect function.
UDP can call the Connect function multiple times.

UDP calls the Connect function:
Send side: We do not need to specify or specify ports and IP addresses again
Receiver: You do not have to use a function like recvfrom to get the sender of the datagram, a connected UDP socket only exchanges data with one IP address
Connected UDP If the error is returned to the sending side
UDP calls the Connect function multiple times:
Specify a new IP and port
Disconnecting sockets

For UDP one-on-one, constantly sending data, can improve efficiency.
Like what:
No connect UDP send data is, establish connection, send data, disconnect, connect, send data, disconnect. Every time a message is sent, a routing query is possible.
The UDP send data of Connect is, send data---Send the data---disconnect.

Test code:
Client:

#include <stdio.h>#include <stdlib.h>#include <assert.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <errno.h>intMainintargcChar*argv[]) {if(ARGC <2){printf("Argument error\n");Exit(1); }Char*ip = argv[1];structsockaddr_in server;structSOCKADDR_IN client;    server.sin_family = af_inet; Server.sin_port = htons (Atoi (argv[2]));    Inet_pton (Af_inet, IP, &server.sin_addr);    client.sin_family = af_inet; Client.sin_port = htons (8000);//Note the native test can be 127.0.0.1, it is not through the network card, non-native test must be designated as the network card external IP address, ifconfig can be viewed. Inet_pton (Af_inet,"192.168.23.3", &AMP;CLIENT.SIN_ADDR);intFD = socket (af_inet, SOCK_DGRAM,0);if(FD <0){printf("Create socket error\n");Exit(1); }intBret = Bind (FD, (structsockaddr*) &client,sizeof(client));if(Bret = =-1){printf("Bind error\n");Exit(1); }intCret = Connect (FD, (structsockaddr*) &server,sizeof(server));if(Cret = =-1){printf("Connect error\n");printf("%d\n", CRET);//If errors can be viewed with error numbers, and errors are seen compared to the tableStrerror (errno);printf("%d\n", errno);Exit(1); }Else{printf("Connect success!\n"); }Charbuf[ +] ="Hello World";intn = sendto (fd, BUF, +,0, (structsockaddr*) &server,sizeof(server));//int n = Write (fd, buf, +);    //int n = sendto (fd, buf, +, 0, NULL, 0);    //int n = Send (fd, buf, 0);    if(N <=0){printf("Send error\n"); }returnexit_success;}

Service side:

#include <stdio.h>#include <stdlib.h>#include <assert.h>#include <sys/socket.h>#include <sys/types.h>#include <string.h>#include <netinet/in.h>#include <arpa/inet.h>intMainintargcChar*argv[]) {if(ARGC <2){printf("Argument error\n"); }intPort = atoi (argv[2]);Char*ip = argv[1];structsockaddr_in server; Bzero (&server,sizeof(server));    server.sin_family = af_inet;    Server.sin_port = htons (port); Inet_pton (Af_inet, IP, &server.sin_addr);intUDPFD = socket (af_inet, SOCK_DGRAM,0);if(UDPFD <0){printf("Socket UDP socketfd error\n");Exit(-1); }intret = bind (UDPFD, (structsockaddr*) &server,sizeof(server));if(ret = =-1){printf("Bind error\n");Exit(-1); }structSOCKADDR_IN client; socklen_t len =sizeof(client);Charbuffer[2048]; while(1) {bzero (buffer,2048);//int n = recvfrom (UDPFD, buffer, 2048, 0, (struct sockaddr*) &client, &len);        intn = read (UDPFD, buffer,2048);printf("%s\n", buffer); }returnexit_success;}

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UDP calls the Connect function