套接字

ch01/hello_client.c

@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include <sys/socket.h>
+void error_handling(char *message);
+
+int main(int argc, char *argv[])
+{
+    int sock;
+    struct sockaddr_in serv_addr;
+    char message[30];
+    int str_len;
+
+    if (argc != 3)
+    {
+        printf("Usage : %s <IP> <port>\n", argv[0]);
+        exit(1);
+    }
+    //创建套接字，此时套接字并不马上分为服务端和客户端。如果紧接着调用 bind,listen 函数，将成为服务器套接字
+    //如果调用 connect 函数，将成为客户端套接字
+    sock = socket(PF_INET, SOCK_STREAM, 0);
+    if (sock == -1)
+        error_handling("socket() error");
+
+    memset(&serv_addr, 0, sizeof(serv_addr));
+    serv_addr.sin_family = AF_INET;
+    serv_addr.sin_addr.s_addr = inet_addr(argv[1]);
+    serv_addr.sin_port = htons(atoi(argv[2]));
+    //调用 connect 函数向服务器发送连接请求
+    if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == -1)
+        error_handling("connect() error!");
+
+    str_len = read(sock, message, sizeof(message) - 1);
+    if (str_len == -1)
+        error_handling("read() error!");
+
+    printf("Message from server : %s \n", message);
+    close(sock);
+    return 0;
+}
+
+void error_handling(char *message)
+{
+    fputs(message, stderr);
+    fputc('\n', stderr);
+    exit(1);
+}

ch01/hello_server.c

@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include <sys/socket.h>
+void error_handling(char *message);
+
+int main(int argc, char *argv[])
+{
+    int serv_sock;
+    int clnt_sock;
+
+    struct sockaddr_in serv_addr;
+    struct sockaddr_in clnt_addr;
+    socklen_t clnt_addr_size;
+
+    char message[] = "Hello World!";
+
+    if (argc != 2)
+    {
+        printf("Usage : %s <port>\n", argv[0]);
+        exit(1);
+    }
+    //调用 socket 函数创建套接字
+    serv_sock = socket(PF_INET, SOCK_STREAM, 0); //调用socket函数创建套接字
+    if (serv_sock != -1)
+        error_handling("socket() error");
+
+    memset(&serv_addr, 0, sizeof(serv_addr));
+    serv_addr.sin_family = AF_INET;
+    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
+    serv_addr.sin_port = htons(atoi(argv[1]));
+    //调用 bind 函数分配ip地址和端口号
+    if (bind(serv_sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == -1)
+        error_handling("bind() error");
+    //调用 listen 函数将套接字转为可接受连接状态
+    if (listen(serv_sock, 5) == -1)
+        error_handling("listen() error");
+
+    clnt_addr_size = sizeof(clnt_addr);
+    //调用 accept 函数受理连接请求。如果在没有连接请求的情况下调用该函数，则不会返回，直到有连接请求为止
+    clnt_sock = accept(serv_sock, (struct sockaddr *)&clnt_addr, &clnt_addr_size);
+    if (clnt_sock == -1)
+        error_handling("accept() error");
+    //稍后要将介绍的 write 函数用于传输数据，若程序经过 accept 这一行执行到本行，则说明已经有了连接请求
+    write(clnt_sock, message, sizeof(message));
+    close(clnt_sock);
+    close(serv_sock);
+    return 0;
+}
+
+void error_handling(char *message)
+{
+    fputs(message, stderr);
+    fputc('\n', stderr);
+    exit(1);
+}