网络编程Socket UDP

图表流程

linux udp测试代码

//server.c
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/un.h>
#include <sys/socket.h>
#include <sys/unistd.h>
#include <arpa/inet.h>

#define PORT        8999
#define MAXSIZE     4096

int main(int argc, char *argv[])
{
    int sockfd, addr_len;
    struct sockaddr_in serv_addr, clnt_addr;
    char recvmsg[MAXSIZE], sendmsg[MAXSIZE];

    sockfd = socket(AF_INET, SOCK_DGRAM, );
    if (sockfd < ) {
        perror("socket error");
        return -;
    }

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);
    serv_addr.sin_addr.s_addr = INADDR_ANY;
    memset(&(serv_addr.sin_zero), ，);

    if (bind(sockfd, (struct sockaddr *)&serv_addr, sizeof(struct sockaddr)) < ) {
        perror("bind err");
        return -;
    }

    while() {
        memset(sendmsg, , MAXSIZE);
        memset(recvmsg, , MAXSIZE);
        addr_len = sizeof(struct sockaddr);
        /* 所谓的非阻塞I/O */
        if (recvfrom(sockfd, recvmsg, MAXSIZE, , (struct sockaddr *)&clnt_addr, &addr_len) < ) {
            perror("recv");
            continue;
        }

        printf("begin to accept\n");
        printf("recv from %s : %s\n", inet_ntoa(clnt_addr.sin_addr), recvmsg);
        strcpy(sendmsg, "who are you ?? Let me cc!");
        sendto(sockfd, sendmsg, strlen(sendmsg) + , , (struct sockaddr *)&clnt_addr, addr_len);
    }

    return ;
}

//client.c
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/un.h>
#include <sys/socket.h>
#include <sys/unistd.h>
#include <arpa/inet.h>

#define PORT        8999
#define DESIP  "192.168.23.109"
#define MAXSIZE     4096

int main(int argc, char *argv[])
{
    int sockfd, addr_len;
    struct sockaddr_in des_addr;
    char sendmsg[MAXSIZE], recvmsg[MAXSIZE]; 

    sockfd = socket(AF_INET, SOCK_DGRAM, );
    if (sockfd < ) {
        perror("socket error");
        return -;
    }

    des_addr.sin_family = AF_INET;
    des_addr.sin_port = htons(PORT);
    des_addr.sin_addr.s_addr = inet_addr(DESIP);
    //bzero(&(des_addr.sin_zero), 8);
    memset(&(des_addr.sin_zero), ,);
    while () {
        memset(recvmsg, , MAXSIZE);
        memset(sendmsg, , MAXSIZE);
        printf("input:\n");
        gets(sendmsg);
        if (strcmp(sendmsg, "quit") == ) {
            close(sockfd);
            printf("close connection\n");
            return -;
        }
        if (sendto(sockfd, sendmsg, strlen(sendmsg) + , , (struct sockaddr *)&des_addr, sizeof(struct sockaddr)) < ) {
            perror("sendto");
            continue;
        }
        printf("send ok...\n");

        while () {/* 所谓的非阻塞I/O */
            addr_len = sizeof(struct sockaddr);
            if (recvfrom(sockfd, recvmsg, MAXSIZE, , (struct sockaddr *)&des_addr, &addr_len) < ) {
                continue;
            }
            printf("recv from %s : %s\n", inet_ntoa(des_addr.sin_addr), recvmsg);
            break;
        }
    }

    return ;
}

参考资料：

Linux的Socket编程详解

Linux Socket编程（不限Linux)