71 lines
2.1 KiB
C
71 lines
2.1 KiB
C
// 编写一个UDP服务器程序，接收客户端发送的字符串，并将其转换为大写后发送回客户端。
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#include <stdio.h>
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#include <arpa/inet.h>
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#include <netinet/in.h>
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#include <unistd.h>
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#include <string.h>
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#include <sys/socket.h>
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#include <ctype.h> // toupper
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int main(int argc, char const *argv[])
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{
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int sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
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if (sock_fd < 0)
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{
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perror("socket");
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return -1;
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}
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struct sockaddr_in addr;
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bzero(&addr, sizeof(addr));
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addr.sin_family = AF_INET;
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addr.sin_port = htons(8000);
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addr.sin_addr.s_addr = htonl(INADDR_ANY);
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if (bind(sock_fd, (struct sockaddr *)&addr, sizeof(addr)) != 0)
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{
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perror("bind");
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}
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else
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{
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printf("bind success\n");
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struct sockaddr_in src_addr;
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char buf[128] = ""; // 接收数据的空间
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socklen_t socklen = sizeof(src_addr);
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while (1)
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{
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bzero(&src_addr, sizeof(src_addr));
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bzero(buf, 128);
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// 接收数据，如果数据未到达，则会阻塞，直到数据到达为止
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ssize_t len = recvfrom(sock_fd, buf, sizeof(buf), 0, (struct sockaddr *)&src_addr, &socklen);
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if (len < 0)
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{
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perror("recvfrom");
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break;
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}
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char srcIP[INET_ADDRSTRLEN]; // 16
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int port = ntohs(src_addr.sin_port); // 将网络字节序转化为本地字节序
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inet_ntop(AF_INET, &src_addr.sin_addr.s_addr, srcIP, INET_ADDRSTRLEN); // 将网络数字转换为点分十进制 ip
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printf("从 %s:%d 位置接收到的数据(%lu Bytes): %s\n", srcIP, port, len, buf);
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int i = 0;
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while (buf[i])
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{
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buf[i] = toupper(buf[i]); // 转大写
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i++;
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}
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sendto(sock_fd, buf, len, 0, (struct sockaddr *)&src_addr, socklen);
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printf("发送回去的消息为 %s\n", buf);
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}
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}
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close(sock_fd);
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return 0;
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}
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