13.1.3 紧急模式工作原理

ch13/README.md

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+13.

ch13/oob_recv.c

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+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <signal.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <fcntl.h>
+
+#define BUF_SIZE 30
+void error_handling(char *message);
+void urg_handler(int signo);
+
+int acpt_sock;
+int recv_sock;
+
+int main(int argc, char *argv[])
+{
+    struct sockaddr_in recv_adr, serv_adr;
+    int str_len, state;
+    socklen_t serv_adr_sz;
+    struct sigaction act;
+    char buf[BUF_SIZE];
+    if (argc != 2)
+    {
+        printf("Usage : %s <port>\n", argv[0]);
+        exit(1);
+    }
+    act.sa_handler = urg_handler;
+    sigemptyset(&act.sa_mask);
+    act.sa_flags = 0;
+
+    acpt_sock = socket(PF_INET, SOCK_STREAM, 0);
+    memset(&recv_adr, 0, sizeof(recv_adr));
+    recv_adr.sin_family = AF_INET;
+    recv_adr.sin_addr.s_addr = htonl(INADDR_ANY);
+    recv_adr.sin_port = htons(atoi(argv[1]));
+
+    if (bind(acpt_sock, (struct sockaddr *)&recv_adr, sizeof(recv_adr)) == -1)
+        error_handling("bind() error");
+    listen(acpt_sock, 5);
+
+    serv_adr_sz = sizeof(serv_adr);
+    recv_sock = accept(acpt_sock, (struct sockaddr *)&serv_adr, &serv_adr_sz);
+    //将文件描述符 recv_sock 指向的套接字拥有者（F_SETOWN）改为把getpid函数返回值用做id的进程
+    fcntl(recv_sock, F_SETOWN, getpid());
+    state = sigaction(SIGURG, &act, 0); //SIGURG 是一个信号，当接收到 MSG_OOB 紧急消息时，系统产生SIGURG信号
+
+    while ((str_len = recv(recv_sock, buf, sizeof(buf), 0)) != 0)
+    {
+        if (str_len == -1)
+            continue;
+        buf[str_len] = 0;
+        puts(buf);
+    }
+    close(recv_sock);
+    close(acpt_sock);
+    return 0;
+}
+void urg_handler(int signo)
+{
+    int str_len;
+    char buf[BUF_SIZE];
+    str_len = recv(recv_sock, buf, sizeof(buf) - 1, MSG_OOB);
+    buf[str_len] = 0;
+    printf("Urgent message: %s \n", buf);
+}
+
+void error_handling(char *message)
+{
+    fputs(message, stderr);
+    fputc('\n', stderr);
+    exit(1);
+}

ch13/oob_send.c

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+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+
+#define BUF_SIZE 30
+void error_handling(char *message);
+
+int main(int argc, char *argv[])
+{
+    int sock;
+    struct sockaddr_in recv_adr;
+    if (argc != 3)
+    {
+        printf("Usage : %s <IP> <port>\n", argv[0]);
+        exit(1);
+    }
+    sock = socket(PF_INET, SOCK_STREAM, 0);
+    memset(&recv_adr, 0, sizeof(recv_adr));
+    recv_adr.sin_family = AF_INET;
+    recv_adr.sin_addr.s_addr = inet_addr(argv[1]);
+    recv_adr.sin_port = htons(atoi(argv[2]));
+
+    if (connect(sock, (struct sockaddr *)&recv_adr, sizeof(recv_adr)) == -1)
+        error_handling("connect() error");
+
+    write(sock, "123", strlen("123"));
+    send(sock, "4", strlen("4"), MSG_OOB);
+    write(sock, "567", strlen("567"));
+    send(sock, "890", strlen("890"), MSG_OOB);
+    close(sock);
+    return 0;
+}
+
+void error_handling(char *message)
+{
+    fputs(message, stderr);
+    fputc('\n', stderr);
+    exit(1);
+}