C：TCP服务器无法接收来自客户端的消息

Question

我是一个C初学者。我想通过 TCP 发送文件。客户端从txt文件中读取内容并将其发送到服务器。读取方法就可以了。它从文件中读取指定的字节。 Send 方法不会抛出任何异常。然而服务器什么也没收到。我尝试了一整天来解决它。我失败了。

请帮我检查一下我的代码有什么问题。

作为评论建议，我再次编辑我的代码。现在有两个问题。一是在客户端循环中，客户端 fread() 和 send() 的返回值前两次都大于 0，而服务器 accept() 仍然处于阻塞状态，没有收到客户端的消息。

第二个问题。在第三个客户端循环中，客户端fread()的返回值仍然大于0，但是send()的返回值是-1。我尝试以二进制模式rb而不是r打开文件。这是同样的问题。

编辑后的客户端代码：

#include <stdio.h>
#include <winsock.h>
#include <time.h>

#pragma comment(lib, "WS2_32.lib")
#define    MAXLINE        1024*4


SOCKET sockClient;// = socket(AF_INET,SOCK_DGRAM,0);
SOCKADDR_IN servAddr;


int main(void) {
    WSADATA wsd;
    FILE *fp;
    int read_len;
    char buf2[MAXLINE];
    time_t t_start, t_end;

    if ((fp = fopen("file.txt", "r")) == NULL) {
        perror("Open file failed\n");
        exit(0);
    }

    if (WSAStartup(MAKEWORD(2, 2), &wsd) != 0) {
        printf("WSAStartup failed !\n");
        return 1;
    }

    sockClient = socket(AF_INET, SOCK_STREAM, 0);

    servAddr.sin_family = AF_INET;
    servAddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
    servAddr.sin_port = htons(5000);

    /* connect the server commanted by guoqingbo*/
    int i_ret = connect(sockClient, (struct sockaddr *) &servAddr, sizeof(struct sockaddr));
    if (-1 == i_ret) {
        perror("Connect socket failed!\n");
        exit(0);
    }

    printf("client starts\n");
    t_start = time(NULL);

    while (1) {
        read_len = fread(buf2, sizeof(char), MAXLINE, fp);
        if (read_len < 0) {
            perror("read data failed\n");
            break;
        } else if (read_len == 0) {
            printf("read finished\n");
        }
        int send_len = send(sockClient, buf2, read_len, 0);
        if (send_len < 0) {
            perror("Send data failed\n");
            exit(0);
        } else if (send_len == 0) {
            printf("send finished\n");
            break;
        }
    }
    t_end = time(NULL);
    printf("The time used %f s\n", difftime(t_end, t_start));
    fclose(fp);
    closesocket(sockClient);
    WSACleanup();
    return 0;
}

编辑后的服务器代码：

#include <stdio.h>
#include <WINSOCK2.H>
#include <strings.h>
#include <stdlib.h>


#pragma comment(lib, "WS2_32.lib")
#define BUF_SIZE    1024*4

SOCKET socketSrv;
SOCKADDR_IN addrSrv;
SOCKADDR_IN addrClient;
char buf[BUF_SIZE];


int main(void) {
    WSADATA wsd;
    int nRet;
    int recv_len;
    FILE *fp;
    if ((fp = fopen("file.txt", "w")) == NULL) {
        perror("Creat file failed");
        exit(0);
    }
    
    if (WSAStartup(MAKEWORD(2, 2), &wsd) != 0) {
        printf("WSAStartup failed !\n");
        return 1;
    }

    socketSrv = socket(AF_INET, SOCK_STREAM, 0);
    int len = sizeof(SOCKADDR);

    ZeroMemory(buf, BUF_SIZE);
    addrSrv.sin_addr.S_un.S_addr = htonl(INADDR_ANY);
    addrSrv.sin_family = AF_INET;
    addrSrv.sin_port = htons(5000);

    nRet = bind(socketSrv, (SOCKADDR *) &addrSrv, sizeof(SOCKADDR));
    if (SOCKET_ERROR == nRet) {
        printf("bind failed !\n");
        closesocket(socketSrv);
        WSACleanup();
        return -1;
    }

    if (SOCKET_ERROR == listen(socketSrv, 10)) {
        printf("Server Listen Failed: %d", WSAGetLastError());
        exit(1);
    }


    printf("server started..\n");
    while (1) {
        SOCKET m_New_Socket = accept(socketSrv, (SOCKADDR *) &addrClient, &len);
        if (SOCKET_ERROR == m_New_Socket) {
            printf("Server Accept Failed: %d", WSAGetLastError());
            break;
        }
        if (recv_len = recv(socketSrv, buf, BUF_SIZE, 0) < 0) {
            printf("Server Receive Data Failed!");
            break;
        }
        int write_length = fwrite(buf, sizeof(char), recv_len, fp);
        if (write_length < recv_len) {
            printf("File write failed\n");
            break;
        }
    }
    fclose(fp);
    closesocket(socketSrv);
    WSACleanup();
    return 0;
}