UDP:
User datagram protocol
Features:
Connectionless protocol, unreliable, data leakage, fast transmission
USES:
(1) Send small-size data: for example, DNS server performs IP address query
(2) in the receiving data, give the response is difficult to use UDP network, such as: some wireless networks
(3) QQ, Feiqiu, MSN, and other instant messaging tools for audio and video data transmission and video conferencing and other related applications
(4) Streaming media, IPTV and other network multimedia services
(5) Broadcast and multicast communication
UDP server and client design ideas
Differences between UDP and TCP
(1) The second parameter of the socket
TCP: stream socket SOCK_STREAM
UDP: datagram socket SOCK_DGRAM
(2) UDP does not need listen,accept and connect
(3) Different data sent and received, such as UDP: recvfrom,sendto
Example Code 1
The server and client send messages to each other
/ / the server
#include <stdio.h>
#include <error.h>
#include <errno.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <pthread.h>
int main(int argc, char const *argv[])
{
// create communication socket // domain datagram socket
int s_socket = socket(AF_INET, SOCK_DGRAM, 0);
if (s_socket == - 1)
{
perror("socket");
return - 1;
}
// Socket set port reuse
int reuse = - 1;
if(setsockopt(s_socket, SOL_SOCKET, SO_REUSEADDR, (void *)&reuse, sizeof(reuse)) < 0)
{
perror("setsockopt error");
return - 1;
}
//2. Initialize address structure
struct sockaddr_in s_addr;
memset(&s_addr, 0.sizeof(s_addr));
s_addr.sin_family = AF_INET; / / address family
s_addr.sin_port = 55628; / / the port number
/ / s_addr. Sin_addr. S_addr = inet_addr (" 192.168.1.235 ");
s_addr.sin_addr.s_addr = htonl(INADDR_ANY);
//3. Bind the local IP address structure of the server to the socket
if(bind(s_socket, (struct sockaddr *)&s_addr, sizeof(struct sockaddr)))
{
perror("bind");
return - 1;
}
printf("Server address binding successful \n");
//4
char r_buf[512];
char w_buf[512];
// Define a structure to store the client address
struct sockaddr_in c_addr;
int len = sizeof(c_addr);
while(1)
{
memset(r_buf, 0.sizeof(r_buf));
memset(w_buf, 0.sizeof(w_buf));
memset(&c_addr, 0.sizeof(c_addr));
recvfrom(s_socket, r_buf, sizeof(r_buf), 0, (struct sockaddr *)&c_addr, &len);
printf("Buf: % s \ n", r_buf);
printf("[%s][%d]\n", inet_ntoa(c_addr.sin_addr), ntohs(c_addr.sin_port));
scanf("%[^\n]", w_buf);
getchar();
sendto(s_socket, w_buf, sizeof(w_buf), 0, (struct sockaddr *)&c_addr, sizeof(c_addr));
}
// close the socket
close(s_socket);
return 0;
}
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#include <stdio.h>
#include <error.h>
#include <errno.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <pthread.h>
int main(int argc, char const *argv[])
{
// create communication socket // domain datagram socket
int c_socket = socket(AF_INET, SOCK_DGRAM, 0);
if (c_socket == - 1)
{
perror("socket");
return - 1;
}
// Socket set port reuse
int reuse = - 1;
if(setsockopt(c_socket, SOL_SOCKET, SO_REUSEADDR, (void *)&reuse, sizeof(reuse)) < 0)
{
perror("setsockopt error");
return - 1;
}
//2. Initialize address structure
struct sockaddr_in c_addr;
memset(&c_addr, 0.sizeof(c_addr));
c_addr.sin_family = AF_INET; / / address family
c_addr.sin_port = 55628; / / the port number
c_addr.sin_addr.s_addr = inet_addr("192.168.1.11");
//3, bind the local IP address structure of the server to the socket (optional)
// if(bind(c_socket, (struct sockaddr *)&c_addr, sizeof(struct sockaddr)))
/ / {
// perror("bind");
// return -1;
// }
// printf(" server address binding successful \n");
//4
char w_buf[512];
char r_buf[512];
// Define a server address structure to store IP addresses and port numbers
struct sockaddr_in s_addr;
int len = sizeof(s_addr);
while(1)
{
memset(w_buf, 0.sizeof(w_buf));
memset(r_buf, 0.sizeof(r_buf));
scanf("%[^\n]", w_buf);
getchar();
sendto(c_socket, w_buf, sizeof(w_buf), 0, ( struct sockaddr *)&c_addr, sizeof(c_addr));
recvfrom(c_socket, r_buf, sizeof(r_buf), 0, (struct sockaddr *)&s_addr, &len);
printf("Buf: % s \ n", r_buf);
printf("[%s][%d]\n", inet_ntoa(s_addr.sin_addr), ntohs(s_addr.sin_port));
}
// close the socket
close(c_socket);
return 0;
}
Copy the codeThe results
Example Code 2
Design a UDP server to achieve:
(1) Initialize the binding server IP, port number, and socket
(2) Circularly receiving messages
1. The client online message displays the IP address and port number of the current online client and records them
2. The chat information on the client is directly forwarded to the peer client
Design a UDP client program, to achieve:
(1) To send an online message when going online
(2) Thread 1: send messages (chat message mark, IP address of the other party, message content)
(3) Thread 2: receive messages and display
/ / the server
#include <stdio.h>
#include <error.h>
#include <errno.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <pthread.h>
#include <stdlib.h>
// Create a list node structure to store address information
typedef struct node
{
struct sockaddr_in client_addr;
struct node *next;
}Node, *List;
// Message structure
struct MSG
{
int flag; //1 indicates the online message, and 2 indicates the chat message
char to_IP[20]; // Indicates the IP address to which the message is sent
char from_IP[20]; // Indicates that the message is from that user IP
char text[1024]; // Message content
};
int main(int argc, char const *argv[])
{
// Initializes an empty list of leading nodes
List caddr_list = malloc(sizeof(Node));
// create communication socket // domain datagram socket
int s_socket = socket(AF_INET, SOCK_DGRAM, 0);
if (s_socket == - 1)
{
perror("socket");
return - 1;
}
// Socket set port reuse
int reuse = - 1;
if(setsockopt(s_socket, SOL_SOCKET, SO_REUSEADDR, (void *)&reuse, sizeof(reuse)) < 0)
{
perror("setsockopt error");
return - 1;
}
//2. Initialize address structure
struct sockaddr_in s_addr;
memset(&s_addr, 0.sizeof(s_addr));
s_addr.sin_family = AF_INET; / / address family
s_addr.sin_port = 55558; / / the port number
/ / s_addr. Sin_addr. S_addr = inet_addr (" 192.168.1.235 ");
s_addr.sin_addr.s_addr = htonl(INADDR_ANY);
//3. Bind the local IP address structure of the server to the socket
if(bind(s_socket, (struct sockaddr *)&s_addr, sizeof(struct sockaddr)))
{
perror("bind");
return - 1;
}
printf("Server address binding successful \n");
//4
struct MSG rmsg;
// Define a structure to store the client address
struct sockaddr_in c_addr;
int len = sizeof(c_addr);
while(1)
{
bzero(&rmsg, sizeof(rmsg));
recvfrom(s_socket, &rmsg, sizeof(rmsg), 0, (struct sockaddr *)&c_addr, &len);
// Client online information
if (rmsg.flag == 1)
{
// Print the user online
printf("User [%s:%d] online \n", inet_ntoa(c_addr.sin_addr), ntohs(c_addr.sin_port));
// Add the user to the list
List new = malloc(sizeof(Node));
if (new= =NULL)
{
printf("Failed to create new node \n");
continue;
}
new->client_addr = c_addr;
new->next = NULL;
// Insert this node into the linked list
new->next = caddr_list->next;
caddr_list->next = new;
printf("New user info logged \n");
}
// Send a message
else
if (rmsg.flag == 2)// Client chat information
{
List p = caddr_list;
while(p->next ! =NULL)
{
p = p->next;
if (strcmp(inet_ntoa(p->client_addr.sin_addr), rmsg.to_IP) == 0)
{
strcpy(rmsg.from_IP, inet_ntoa(c_addr.sin_addr));
sendto(s_socket, &rmsg, sizeof(rmsg), 0,
(struct sockaddr *)&(p->client_addr),
sizeof(struct sockaddr_in)); }}}// else
// if (rmsg.flag == 3)// Offline
/ / {
// // Find the source address of the message, remove it from the linked list, and print XXX offline
// }
}
// close the socket
close(s_socket);
return 0;
}
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#include <stdio.h>
#include <error.h>
#include <errno.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <pthread.h>
// Message structure
struct MSG
{
int flag; //1 indicates the online message, and 2 indicates the chat message
char to_IP[20]; // Indicates the IP address to which the message is sent
char from_IP[20]; // Indicates that the message is from that user IP
char text[1024]; // Message content
};
void *recv_msg(void *arg)
{
int c_socket = *(int *)arg;
// Define a server address structure to store IP addresses and port numbers
struct sockaddr_in s_addr;
int len = sizeof(s_addr);
struct MSG rmsg;
while(1)
{
memset(&s_addr, 0.sizeof(s_addr));
memset(&rmsg, 0.sizeof(rmsg));
recvfrom(c_socket, &rmsg, sizeof(rmsg), 0, (struct sockaddr *)&s_addr, &len);
printf("-------------------------------------------\n");
printf("Message from [%s] : %s\n", rmsg.from_IP, rmsg.text);
printf("-------------------------------------------\n"); }}int main(int argc, char const *argv[])
{
// create communication socket // domain datagram socket
int c_socket = socket(AF_INET, SOCK_DGRAM, 0);
if (c_socket == - 1)
{
perror("socket");
return - 1;
}
// Socket set port reuse
int reuse = - 1;
if(setsockopt(c_socket, SOL_SOCKET, SO_REUSEADDR, (void *)&reuse, sizeof(reuse)) < 0)
{
perror("setsockopt error");
return - 1;
}
//2. Initialize address structure
struct sockaddr_in c_addr;
memset(&c_addr, 0.sizeof(c_addr));
c_addr.sin_family = AF_INET; / / address family
c_addr.sin_port = 55558; / / the port number
c_addr.sin_addr.s_addr = inet_addr("192.168.1.235");
// Send an online message first
struct MSG one_msg = {1.""."".""};
sendto(c_socket, &one_msg, sizeof(one_msg), 0, ( struct sockaddr *)&c_addr, sizeof(c_addr));
//4
struct MSG smsg;
pthread_t pid;
pthread_create(&pid, NULL, recv_msg, (void *)&c_socket);
while(1)
{
memset(&smsg, 0.sizeof(smsg));
smsg.flag = 2;
scanf("%s%s", smsg.to_IP, smsg.text);
getchar();
sendto(c_socket, &smsg, sizeof(smsg), 0, ( struct sockaddr *)&c_addr, sizeof(c_addr));
printf("Send successful \n");
}
// close the socket
close(c_socket);
return 0;
}
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