udp

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#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/types.h>#include <netinet/in.h>#include <sys/socket.h>#include <arpa/inet.h>#include <unistd.h>int main(int argc, char *argv[]){    int sock;    //sendto中使用的对方地址    struct sockaddr_in toAddr;    //在recvfrom中使用的对方主机地址    struct sockaddr_in fromAddr;    int recvLen;    unsigned int addrLen;    char recvBuffer[128];    sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);    if(sock < 0)    {        printf("创建套接字失败了.\r\n");        exit(0);    }    memset(&fromAddr, 0, sizeof(fromAddr));    fromAddr.sin_family = AF_INET;    fromAddr.sin_addr.s_addr = htonl(INADDR_ANY);    fromAddr.sin_port = htons(4000);    if(bind(sock, (struct sockaddr *)&fromAddr, sizeof(fromAddr)) < 0)    {        printf("bind() 函数使用失败了.\r\n");        close(sock);        exit(1);    }    while(1)    {        addrLen = sizeof(toAddr);        if((recvLen = recvfrom(sock, recvBuffer, 128, 0, (struct sockaddr *)&toAddr, &addrLen)) < 0)        {            printf("()recvfrom()函数使用失败了.\r\n");            close(sock);            exit(1);        }        if(sendto(sock, recvBuffer, recvLen, 0, (struct sockaddr *)&toAddr, sizeof(toAddr)) != recvLen)        {            printf("sendto fail\r\n");            close(sock);            exit(0);        }        return 0;    }}
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