commit 6d6d3a393dbb00b6e6c55c25d237d3f66748b03c
Author: flykhan <liubo666666@outlook.com>
Date:   Tue Sep 5 20:54:17 2023 +0800

    第2天上课

diff --git a/day2/n1.c b/day2/n1.c
new file mode 100644
index 0000000..96a9851
--- /dev/null
+++ b/day2/n1.c
@@ -0,0 +1,23 @@
+#include <stdio.h>
+
+union
+{
+    unsigned short num;
+    unsigned char c[2];
+} data;
+
+int main(int argc, char const *argv[])
+{
+    data.num = 0x0102;
+
+    if (data.c[0] == 1)
+    {
+        printf("大端字节序\n");
+    }
+    else
+    {
+        printf("小端字节序\n");
+    }
+
+    return 0;
+}
diff --git a/day2/n2.c b/day2/n2.c
new file mode 100644
index 0000000..f520079
--- /dev/null
+++ b/day2/n2.c
@@ -0,0 +1,13 @@
+#include <stdio.h>
+#include <arpa/inet.h>
+
+int main(int argc, char const *argv[])
+{
+    unsigned int data=0x01020304;
+    // 转成网络端数据（小端转大端）
+    u_int32_t data2 =  htonl(data);
+    printf("主机字节序: %#x\n",data);
+    printf("网络字节序: %#x\n",data2);
+
+    return 0;
+}
diff --git a/day2/n3.c b/day2/n3.c
new file mode 100644
index 0000000..fe5fdc9
--- /dev/null
+++ b/day2/n3.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+#include <arpa/inet.h>
+
+int main(int argc, char const *argv[])
+{
+    unsigned int data = 0x01020304;
+    // 转成网络端数据（小端转大端）
+    uint32_t data2 = htonl(data);
+    printf("主机字节序: %#08x\n", data);
+    printf("网络字节序: %#x\n", data2);
+
+    // 将网络字节序转为主机字节序
+    uint32_t data3 = ntohl(data2);
+    printf("转换后主机字节序: %#x\n", data);
+
+    return 0;
+}
diff --git a/day2/n4.c b/day2/n4.c
new file mode 100644
index 0000000..5f74acf
--- /dev/null
+++ b/day2/n4.c
@@ -0,0 +1,22 @@
+#include <stdio.h>
+#include <arpa/inet.h>
+
+int main(int argc, char const *argv[])
+{
+    char *ip = "10.35.188.66";
+    // ip 地址转换为四字节
+    uint32_t ip_data;
+
+    // 将 ip 转换为数值
+    int ret = inet_pton(AF_INET, ip, &ip_data);
+    printf("ip转换数值的结果(%d): %#x\n", ret, ip_data);
+
+    // 将 ip 的数值转换为 ipv6 字符串
+    char ip_dst[25] = "";
+    if (inet_ntop(AF_INET6, &ip_data, ip_dst, INET6_ADDRSTRLEN) != NULL)
+    {
+        printf("由数值转化为 ip 地址的字符串: %s\n", ip_dst);
+    }
+
+    return 0;
+}
diff --git a/day2/n5.c b/day2/n5.c
new file mode 100644
index 0000000..db0480b
--- /dev/null
+++ b/day2/n5.c
@@ -0,0 +1,20 @@
+#include <stdio.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+int main(int argc, char const *argv[])
+{
+
+    // 创建socket
+    int socket_fd = socket(AF_INET, SOCK_DGRAM, 0);
+    if (socket_fd < 0)
+    {
+        perror("socket");
+        return 1;
+    }
+    printf("socket 创建成功: %d\n", socket_fd);
+
+    close(socket_fd);
+
+    return 0;
+}
diff --git a/day2/n6_send.c b/day2/n6_send.c
new file mode 100644
index 0000000..865889a
--- /dev/null
+++ b/day2/n6_send.c
@@ -0,0 +1,42 @@
+#include <stdio.h>
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <netinet/in.h> // 地址结构
+#include <unistd.h>
+#include <string.h>
+
+int main(int argc, char const *argv[])
+{
+    // 1. 创建套接字
+    int sfd = socket(AF_INET, SOCK_DGRAM, 0);
+    if (sfd < 0)
+    {
+        perror("socket");
+        return -1;
+    }
+
+    // 2. 创建发送目标的ip地址和端口号
+    struct sockaddr_in addr;
+    bzero(&addr, sizeof(addr)); // 初始化置零
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(8000);
+    inet_pton(AF_INET, "10.35.188.66", &addr.sin_addr.s_addr);
+
+    // 3. 创建发送的数据
+    char *buf = "hi, udp server: disen hh";
+
+    // 4. 发送一次 udp 数据
+    ssize_t n = sendto(sfd, buf, strlen(buf), 0, (struct sockaddr *)&addr, sizeof(addr));
+    if (n > 0)
+    {
+        printf("发送 udp 数据成功\n");
+    }else{
+        printf("发送失败\n");
+        perror("sendto");
+    }
+
+    // 5. 关闭 socket
+    close(sfd);
+
+    return 0;
+}
diff --git a/day2/n6_send_2.c b/day2/n6_send_2.c
new file mode 100644
index 0000000..3cc72b6
--- /dev/null
+++ b/day2/n6_send_2.c
@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <netinet/in.h> // 地址结构
+#include <unistd.h>
+#include <string.h>
+
+int main(int argc, char const *argv[])
+{
+    // 1. 创建套接字
+    int sfd = socket(AF_INET, SOCK_DGRAM, 0);
+    if (sfd < 0)
+    {
+        perror("socket");
+        return -1;
+    }
+
+    // 2. 创建发送目标的ip地址和端口号
+    struct sockaddr_in addr;
+    bzero(&addr, sizeof(addr)); // 初始化置零
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(8000);
+    inet_pton(AF_INET, "192.168.31.1", &addr.sin_addr.s_addr);
+
+    int n = 1;
+
+    // 3. 创建发送的数据
+    while (1)
+    {
+        char buf[128] = "";
+        scanf("%s", buf);
+        if (strncmp(buf, "exit", 4) == 0)
+        {
+            break;
+        }
+        // sprintf(buf, "this is : %lld\n", (n++ * ++n));
+
+        // 4. 发送一次 udp 数据
+        ssize_t n = sendto(sfd, buf, strlen(buf), 0, (struct sockaddr *)&addr, sizeof(addr));
+        if (n > 0)
+        {
+            printf("%s: 发送 udp 数据成功\n", buf);
+        }
+        else
+        {
+            printf("%s: 发送失败\n", buf);
+            perror("sendto");
+        }
+    }
+
+    // 5. 关闭 socket
+    close(sfd);
+
+    return 0;
+}
diff --git a/day2/n7.c b/day2/n7.c
new file mode 100644
index 0000000..7033f9c
--- /dev/null
+++ b/day2/n7.c
@@ -0,0 +1,69 @@
+#include <stdio.h>
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <unistd.h>
+#include <string.h>
+
+int main(int argc, char const *argv[])
+{
+    int sfd = socket(AF_INET, SOCK_DGRAM, 0);
+    if (sfd < 0)
+    {
+        perror("socket");
+        return -1;
+    }
+
+    // 1. 绑定本地 ip 和端口号
+    struct sockaddr_in addr; // sockaddr_in 结构体对象
+    bzero(&addr, sizeof(addr));
+
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(8000);              // 当前 Linux 进程的端口号
+    addr.sin_addr.s_addr = htonl(INADDR_ANY); // INADDR_ANY 任意连接的 ip 可用
+    // inet_pton(AF_INET, "192.168.31.128", &addr.sin_addr.s_addr);
+
+    if (bind(sfd, (struct sockaddr *)&addr, sizeof(addr)) != 0) // 绑定
+    {
+        perror("bind");
+    }
+    else
+    {
+        printf("bind success\n");
+
+        // 接收数据
+        char buf[128] = "";          // 接收数据的空间
+        struct sockaddr_in src_addr; // 数据来源的地址
+        socklen_t addr_len;
+        while (1)
+        {
+            // 重置数据
+            bzero(&src_addr, sizeof(src_addr));
+            bzero(buf, 128);
+
+            // 接收数据，如果数据未到达，则会阻塞，直到数据到达为止
+            socklen_t addr_len = sizeof(src_addr);
+            ssize_t len = recvfrom(sfd, buf, 128, 0, (struct sockaddr *)&src_addr, &addr_len);
+            if (len < 0)
+            {
+                perror("recvfrom");
+                break;
+            }
+
+            char src_ip[16];
+            int src_port = ntohs(src_addr.sin_port);                   // 将网络字节序转化为主机字节序
+            inet_ntop(AF_INET, &src_addr.sin_addr.s_addr, src_ip, 16); // 从 src_addr 取 ip 并转化为字符串赋值给 src_ip
+
+            printf("从 %s:%d 位置接受到的数据(%ld Bytes): %s\n", src_ip, src_port, len, buf);
+
+            char buf2[1280];
+            sprintf(buf2, "返回: %s\n", buf);
+            // 回一句消息
+            sendto(sfd, buf2, strlen(buf2), 0, (struct sockaddr *)&src_addr, addr_len);
+        }
+    }
+
+    close(sfd);
+
+    return 0;
+}
diff --git a/day2/qq/qq.c b/day2/qq/qq.c
new file mode 100644
index 0000000..8d662cb
--- /dev/null
+++ b/day2/qq/qq.c
@@ -0,0 +1,144 @@
+#include <stdio.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <sys/socket.h>
+#include <unistd.h>
+#include <string.h>
+#include <pthread.h>
+#include <stdlib.h> // atoi
+
+void *recv_task(void *arg); // 接收数据的线程任务函数
+void *send_task(void *arg); // 发送数据的线程任务函数
+
+int main(int argc, char const *argv[])
+{
+    if (argc != 2)
+    {
+        printf("usage: %s port\n", argv[0]);
+        return 1;
+    }
+
+    int sfd = socket(AF_INET, SOCK_DGRAM, 0);
+    if (sfd < 0)
+    {
+        perror("socket");
+        return -1;
+    }
+
+    // 绑定 ip 和端口号 (开启 UDP 服务)
+    struct sockaddr_in bind_addr;
+    bzero(&bind_addr, sizeof(bind_addr));
+    bind_addr.sin_family = AF_INET;
+    bind_addr.sin_port = htons(atoi(argv[1]));
+    bind_addr.sin_addr.s_addr = htonl(INADDR_ANY); // 主机 ip 中的任意一个都可以使用
+
+    if (bind(sfd, (struct sockaddr *)&bind_addr, sizeof(bind_addr)) != 0)
+    {
+        perror("bind");
+        close(sfd);
+        return -1;
+    }
+
+    pthread_t t1, t2;
+    pthread_create(&t1, NULL, recv_task, (void *)&sfd);
+    pthread_create(&t2, NULL, send_task, &sfd);
+
+    pthread_join(t2, NULL);
+    pthread_cancel(t1);     // 发完后，取消接收
+    pthread_join(t1, NULL); // 等待接收线程结束
+
+    close(sfd);
+
+    return 0;
+}
+
+void *recv_task(void *arg)
+{
+    int sock_fd = *((int *)arg); // 取出传入的 socket 描述符
+    printf("启动recv_task %d\n", sock_fd);
+    char buf[128] = "";
+    struct sockaddr_in src_addr; // 发送数据的源地址
+    socklen_t sock_len;          // 原地址 socket 的长度
+
+    while (1)
+    {
+        bzero(buf, sizeof(buf));
+        bzero(&src_addr, sizeof(src_addr));
+
+        ssize_t len = recvfrom(sock_fd, buf, sizeof(buf), 0, (struct sockaddr *)&src_addr, &sock_len);
+        if (len < 0)
+        {
+            perror("recvfrom");
+        }
+
+        char ip[INET_ADDRSTRLEN] = "";
+        int port = ntohs(src_addr.sin_port);
+        inet_ntop(AF_INET, &src_addr.sin_addr.s_addr, ip, INET_ADDRSTRLEN);
+
+        printf("%s:%d 说: %s\n", ip, port, buf);
+    }
+}
+
+void *send_task(void *arg)
+{
+    int sock_fd = *((int *)arg);
+    // @192.168.1.2:8000
+    // hi,hello
+    // good,disen
+    // haha
+    // yes
+    // @:8500
+    // very,good
+
+    char ip[INET_ADDRSTRLEN] = "";
+    int port = 0;
+    struct sockaddr_in dst_addr; // 目标地址
+    while (1)
+    {
+        char buf[128] = "";
+        fgets(buf, sizeof(buf), stdin);
+        buf[strlen(buf) - 1] = 0; // 去掉最后的换行
+
+        if (buf[0] == '@')
+        {
+            if (buf[1] == ':')
+            {
+                strcpy(ip, "127.0.0.1");
+                port = atoi(buf + 2);
+            }
+            else
+            {
+                strcpy(ip, strtok(buf + 1, ":"));
+                port = atoi(strtok(NULL, ":"));
+            }
+
+            printf("ip:port is %s:%d\n",ip,port);
+            // 重置
+            bzero(&dst_addr, sizeof(dst_addr));
+            dst_addr.sin_family = AF_INET;
+            dst_addr.sin_port = htons(port);
+            // inet_pton(AF_INET, ip, &dst_addr.sin_addr.s_addr); // 按ipv4转地址
+            dst_addr.sin_addr.s_addr = inet_addr(ip);
+            // inet_pton(sock_fd, ip, &dst_addr.sin_addr.s_addr); // bug地方
+        }
+        else
+        {
+            if (strncmp(buf, "exit", 4) == 0)
+            {
+                break;
+            }
+
+            if (port == 0)
+            {
+                printf("请先确认发送的目的ip和端口号\n");
+                continue;
+            }
+
+            // 发送数据
+            if (sendto(sock_fd, buf, strlen(buf), 0, (struct sockaddr *)&dst_addr, sizeof(dst_addr)) < 0)
+            {
+                perror("sendto");
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/day2/test2.c b/day2/test2.c
new file mode 100644
index 0000000..2051932
--- /dev/null
+++ b/day2/test2.c
@@ -0,0 +1,33 @@
+#include <stdio.h>
+#include <arpa/inet.h>
+
+int main(int argc, char const *argv[])
+{
+    unsigned int data = 0x01020304;
+    printf("主机字节序: ");
+    for (int i = 0; i < sizeof(unsigned int); i++) {
+        unsigned char byte = (data >> (i * 8)) & 0xFF;
+        printf("%02x", byte);
+    }
+    printf("\n");
+
+    // 转成网络字节序（小端转大端）
+    uint32_t data2 = htonl(data);
+    printf("网络字节序: ");
+    for (int i = 0; i < sizeof(uint32_t); i++) {
+        unsigned char byte = (data2 >> (i * 8)) & 0xFF;
+        printf("%02x", byte);
+    }
+    printf("\n");
+
+    // 将网络字节序转为主机字节序
+    uint32_t data3 = ntohl(data2);
+    printf("转换后主机字节序: ");
+    for (int i = 0; i < sizeof(uint32_t); i++) {
+        unsigned char byte = (data3 >> (i * 8)) & 0xFF;
+        printf("%02x", byte);
+    }
+    printf("\n");
+
+    return 0;
+}