C套接字编程,服务器发送缓冲区似乎不被清除

Question

我是socket编程的新手,我遇到了麻烦.我想实现一个服务器,它根据某个客户端请求来回答.在我的情况下,GET,HEAD或其他错误.考虑以下代码

如果我在打电话之前打印答案send()(参见下面的服务器端代码),则消息是正确的.但是,我要从我发送的客户端说

1. 得到
2. 头
3. 得到
4. 测试
5. 得到

,从客户端打印的答案是

You want GET
You want HEAD
You want GETD
HTTP/1.1 400 Bad Request
You want GET Bad Request

因此,似乎从服务器发送的消息有点"覆盖",但这怎么可以避免呢？是否可以"清除服务器缓冲区",如果这是问题呢？

这是完整的服务器端代码

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#define BUFSIZE         1024
#define MAXPENDING      100

int main(){

    char get[] = "GET";
    char head[] = "HEAD";
    int serverSocket = socket(PF_INET, SOCK_STREAM, 0);

    struct sockaddr_in serverAddress;
    serverAddress.sin_family = AF_INET;
    serverAddress.sin_port = htons(8080);
    serverAddress.sin_addr.s_addr = htonl(INADDR_ANY);
    memset(&serverAddress.sin_zero, '\0', 8);

    bind(serverSocket, (struct sockaddr*)&serverAddress, sizeof(serverAddress));

    listen(serverSocket, MAXPENDING);

    for(;;){
        struct sockaddr_in clientAddress;
        int clientAddressLength = sizeof(clientAddress);
        int clientSocket;

        clientSocket = accept(serverSocket, (struct sockaddr*)&clientAddress, &clientAddressLength);

        char buf[BUFSIZE];
        int bytesRec;

        bytesRec = recv(clientSocket, buf, BUFSIZE, 0);
        while(bytesRec > 0){

            char *result;
            result = strtok(buf, " ");

            printf("result %s\n", result);

            if(strcmp(&buf, &get) == 0){
                char answer[] = "You want GET";
                send(clientSocket, answer, strlen(answer), 0);
            }else{
                if(strcmp(&buf, &head) == 0){
                    char answer[] = "You want HEAD";
                    send(clientSocket, answer, strlen(answer), 0);
                }else{
                    char answer[] = "HTTP/1.1 400 Bad Request";
                    send(clientSocket, answer, strlen(answer), 0); 
                }
            }

            bytesRec = recv(clientSocket, buf, BUFSIZE, 0);
        }

    return 0;
}

和客户端

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

int main(){

    int clientSocket = socket(PF_INET, SOCK_STREAM, 0);

    struct sockaddr_in clientAddress;
    clientAddress.sin_family = AF_INET;
    clientAddress.sin_port = 0;
    clientAddress.sin_addr.s_addr = htonl(INADDR_ANY);
    memset(&clientAddress.sin_zero, '\0', 8/*sizeof(clientAddress.sin_zero)*/);

    bind(clientSocket, (struct sockaddr*)&clientAddress, sizeof(clientAddress));

    struct sockaddr_in serverAddress;
    serverAddress.sin_family = AF_INET;
    serverAddress.sin_port = htons(8080);
    serverAddress.sin_addr.s_addr = inet_addr("127.0.0.1");
    memset(&serverAddress.sin_zero, '\0', 8);

    if(connect(clientSocket, (struct sockaddr*)&serverAddress, sizeof(serverAddress)) == -1){
        printf("error in connecting!\n");
        return 0;
    }

    char* serverReply[1024];

    for(;;){
        char request[100];
        printf("Enter your request: ");
        scanf("%s", &request);
        send(clientSocket, request, strlen(msg), 0);
        if(recv(clientSocket, serverReply, strlen(serverReply), 0) < 0){
            printf("failure in receiving from server!\n");
        }else{
            printf("%s\n", serverReply);
        }
    }

    close(clientSocket);

    return 0;
}

Answer 1

send(clientSocket, request, strlen(msg), 0);

这仅发送字符串字符,不包括终止NULL.接收缓冲区不会终止服务器端收到的字符串.

这就是您仍然看到上一条消息中的"D"字符的原因.

You want GETD <-- 'D' is from the previous 'HEAD'

终止服务器上收到的字符串,

buf[bytesRec] = '\0';

编辑:正如@Zan指出的那样,不要这样做:

或者从客户端发送NULL终止符.

send(clientSocket, request, strlen(msg) + 1, 0);