补充socket编程的例子

Author: AlanMelody

source/basic/network/Socket-Programming-Basic.md

@@ -7,6 +7,226 @@ Socket 还可以认为是一种网络间不同计算机上的进程通信的一
 
 Socket 起源于 Unix ，Unix/Linux 基本哲学之一就是“一切皆文件”，都可以用“打开(open) –> 读写(write/read) –> 关闭(close)”模式来进行操作。因此 Socket 也被处理为一种特殊的文件。
 
+## 写一个简易的 WebServer
+
+一个简易的 Server 的流程如下：
+
+- 1.建立连接，接受一个客户端连接。
+- 2.接受请求，从网络中读取一条 HTTP 请求报文。
+- 3.处理请求，访问资源。
+- 4.构建响应，创建带有 header 的 HTTP 响应报文。
+- 5.发送响应，传给客户端。
+
+省略流程 3，大体的程序与调用的函数逻辑如下：
+
+- socket() 创建套接字
+- bind() 分配套接字地址
+- listen() 等待连接请求
+- accept() 允许连接请求
+- read()/write() 数据交换
+- close() 关闭连接
+
+代码如下：
+
+```cpp
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <string>
+#include <cstring>
+#include <iostream>
+
+using namespace std;
+
+const int port = 9090;
+const int buffer_size = 1<<20;
+const int method_size = 1<<10;
+const int filename_size = 1<<10;
+const int common_buffer_size = 1<<10;
+
+void handleError(const string &message);
+void requestHandling(int *sock);
+void sendError(int *sock);
+void sendData(int *sock, char *filename);
+void sendHTML(int *sock, char *filename);
+void sendJPG(int *sock, char *filename);
+
+int main()
+{
+	int server_sock;
+	int client_sock;
+	
+	struct sockaddr_in server_address;
+	struct sockaddr_in client_address;
+
+	socklen_t client_address_size;
+
+    server_sock = socket(PF_INET, SOCK_STREAM, 0);
+
+    if (server_sock == -1)
+    {
+    	handleError("socket error");
+    }
+
+    memset(&server_address,0,sizeof(server_address));
+    server_address.sin_family = AF_INET;
+    server_address.sin_addr.s_addr = htonl(INADDR_ANY);
+    server_address.sin_port = htons(port);
+
+    if(bind(server_sock,(struct sockaddr*)&server_address, sizeof(server_address)) == -1){
+    	handleError("bind error");
+    }
+
+    if(listen(server_sock, 5) == -1) {
+    	handleError("listen error");
+    }
+
+    while(true) {
+        client_address_size = sizeof(client_address);
+        client_sock = accept(server_sock, (struct sockaddr*) &client_address, &client_address_size);
+
+        if (client_sock == -1) {
+            handleError("accept error");
+        }
+        requestHandling(&client_sock);
+    }
+
+    //system("open http://127.0.0.1:9090/index.html");
+    close(server_sock);
+
+	return 0;
+}
+
+void requestHandling(int *sock){
+    int client_sock = *sock;
+    char buffer[buffer_size];
+    char method[method_size];
+    char filename[filename_size];
+
+    read(client_sock, buffer, sizeof(buffer)-1);
+
+    if(!strstr(buffer, "HTTP/")) {
+        sendError(sock);
+        close(client_sock);
+        return;
+    }
+    
+    strcpy(method, strtok(buffer," /"));
+    strcpy(filename, strtok(NULL, " /"));
+
+    if(0 != strcmp(method, "GET")) {
+        sendError(sock);
+        close(client_sock);
+        return;
+    }
+
+    sendData(sock, filename);
+}
+
+void sendData(int *sock, char *filename) {
+    int client_sock = *sock;
+    char buffer[common_buffer_size];
+    char type[common_buffer_size];
+
+    strcpy(buffer, filename);
+
+    strtok(buffer, ".");
+    strcpy(type, strtok(NULL, "."));
+    
+    if(0 == strcmp(type, "html")){
+        sendHTML(sock, filename);
+    }else if(0 == strcmp(type, "jpg")){
+        sendJPG(sock, filename);
+    }else{
+        sendError(sock);
+        close(client_sock);
+        return ;
+    }
+}
+
+void sendHTML(int *sock, char *filename) {
+    int client_sock = *sock;
+    char buffer[buffer_size];
+    FILE *fp;
+
+    char status[] = "HTTP/1.0 200 OK\r\n";
+    char header[] = "Server: A Simple Web Server\r\nContent-Type: text/html\r\n\r\n";
+
+    write(client_sock, status, strlen(status));
+    write(client_sock, header, strlen(header));
+
+    fp = fopen(filename, "r");
+    if(!fp){
+        sendError(sock);
+        close(client_sock);
+        handleError("failed to open file");
+        return ;
+    }
+
+    fgets(buffer,sizeof(buffer), fp);
+    while(!feof(fp)) {
+        write(client_sock, buffer, strlen(buffer));
+        fgets(buffer, sizeof(buffer), fp);
+    }
+
+    fclose(fp);
+    close(client_sock);
+}
+
+void sendJPG(int *sock, char *filename) {
+    int client_sock = *sock;
+    char buffer[buffer_size];
+    FILE *fp;
+    FILE *fw;
+
+    char status[] = "HTTP/1.0 200 OK\r\n";
+    char header[] = "Server: A Simple Web Server\r\nContent-Type: image/jpeg\r\n\r\n";
+
+    write(client_sock, status, strlen(status));
+    write(client_sock, header, strlen(header));
+
+    fp = fopen(filename, "rb");
+    if(NULL == fp){
+        sendError(sock);
+        close(client_sock);
+        handleError("failed to open file");
+        return ;
+    }
+
+    fw = fdopen(client_sock, "w");
+    fread(buffer, 1, sizeof(buffer), fp);
+    while (!feof(fp)){
+        fwrite(buffer, 1, sizeof(buffer), fw);
+        fread(buffer, 1, sizeof(buffer), fp);
+    }
+
+    fclose(fw);
+    fclose(fp);
+    close(client_sock);
+}
+
+void handleError(const string &message) {
+	cout<<message;
+	exit(1);
+}
+
+void sendError(int *sock){
+    int client_sock = *sock;
+
+    char status[] = "HTTP/1.0 400 Bad Request\r\n";
+    char header[] = "Server: A Simple Web Server\r\nContent-Type: text/html\r\n\r\n";
+    char body[] = "<html><head><title>Bad Request</title></head><body><p>400 Bad Request</p></body></html>";
+
+    write(client_sock, status, sizeof(status));
+    write(client_sock, header, sizeof(header));
+    write(client_sock, body, sizeof(body));
+}
+```
+
+
 ### 参考资料
 
 1. [Linux Socket编程](http://www.cnblogs.com/skynet/archive/2010/12/12/1903949.html)