linux select()详解( 二）-- UDP最简实例

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通过本文你会了解到：
1. UDP server的实例
2. UDP client的实例
3. UDP server和client的运行测试

UDP server实例(server.c)

#include <stdio.h>#include <unistd.h>#include <stdlib.h>#include <sys/time.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <string.h>#include <errno.h>//macro#define BUF_SIZE 1024 #define PORT 1025 #undef handle_error#define handle_error(msg) \    do { perror(msg); exit(EXIT_FAILURE); } while(0)int main(int argc, char *argv[]){    struct sockaddr_in server_addr;    fd_set read_fds;    socklen_t len;    char buf[BUF_SIZE];    int server_fd = -1;    int ret;    if((server_fd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)        handle_error("socket");    memset(&server_addr, 0, sizeof(struct sockaddr_in));    server_addr.sin_family = AF_INET;    server_addr.sin_port = htons(PORT);    server_addr.sin_addr.s_addr = htonl(INADDR_ANY); /*any ip*/    if(bind(server_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1)        handle_error("bind");    printf("accepting connections on port %d\n", PORT);    while(1) {        FD_ZERO(&read_fds);        FD_SET(server_fd ,&read_fds);        ret = select(server_fd + 1, &read_fds, NULL, NULL, NULL);        if(ret == -1 && errno == EINTR)            continue;        if(ret == -1)            handle_error("select");        if(ret == 0) /*timeout, if you set timeout.*/            continue;        if(FD_ISSET(server_fd, &read_fds)) {            memset(buf, 0, BUF_SIZE);            len = sizeof(server_addr);            if(recvfrom(server_fd, (void *)buf, BUF_SIZE, 0, (struct sockaddr *)&server_addr, &len) > 0) {                printf("Receive packet from %s:%d\nData:%s\n",                         inet_ntoa(server_addr.sin_addr),                        ntohs(server_addr.sin_port),                        buf);            } else {                handle_error("recvfrom");            }        }    }    close(server_fd);    return 0;}

UDP client实例(client.c)

#include <stdio.h>#include <unistd.h>#include <stdlib.h>#include <sys/types.h>#include <sys/time.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <sys/un.h>#include <string.h>#include <pthread.h>#include <errno.h>//macro#define BUF_SIZE 1024 #define PORT 1025 #define SEND_PACK_CNT 3#define SRV_IP "127.0.0.1" #undef handle_error#define handle_error(msg) \    do { perror(msg); exit(EXIT_FAILURE); } while(0)int main(int argc, char *argv[]){    struct sockaddr_in server_addr;    char buf[BUF_SIZE];    int server_fd = -1;    int i;    if((server_fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)        handle_error("socket");    memset(&server_addr, 0, sizeof(struct sockaddr_in));    server_addr.sin_family = AF_INET;    server_addr.sin_port = htons(PORT);    if (inet_aton(SRV_IP, &server_addr.sin_addr) == 0)        handle_error("inet_aton");    for(i = 0; i < SEND_PACK_CNT; i++) {        sprintf(buf, "Packet %d", i);        sendto(server_fd, buf, strlen(buf) + 1, 0, (struct sockaddr *)&server_addr, sizeof(server_addr));    }    close(server_fd);    return 0;}

运行测试
编译
gcc server.c -o server
gcc client.c -o client

server端运行结果

#./serveraccepting connections on port 1025/*下列内容时运行client后，server端收到的数据包后的打印信息*/Receive packet from 127.0.0.1:34833Data:Packet 0Receive packet from 127.0.0.1:34833Data:Packet 1Receive packet from 127.0.0.1:34833Data:Packet 2

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