c - TCP 服务器-客户端在单次传输后断开连接

Question

我正在为学校开发一个服务器-客户端程序，并使用给定的代码进行 TCP 连接。 客户端:

void func(int sockfd) 
{ 
char entryArr[MAXSIZE][MAXLEN];
int n,c;
int i = 0;
char entry;
char iEntry[1];
char id[6];
char fname[5];
char lname[5];
char score[4];
for (;;) { 
    bzero(id, sizeof(id));
    bzero(fname, sizeof(fname));
    bzero(lname, sizeof(lname));
    bzero(score, sizeof(score));    
    printf("[1] Add a Student \n");     //Menu
    printf("[2] Display ID \n");
    printf("[3] Display Score \n");
    printf("[4] Display All \n");
    printf("[5] Delete an Entry \n");
    printf("[6] Exit \n");
    printf("Please Select from the Menu: ");  //get menu selection
    scanf("%1s", iEntry);   //read entry

    if (iEntry[0] == '1') //if entry = 1
    {
        getchar();
        printf("\n------Add a New Student------  \n"); 
        printf("\n6-Digit ID: "); 
        scanf("%6s", id);           //read 6 digit id

        while ( (c = getchar()) != '\n' && c != EOF );
        printf("Student's First Name: "); 
        scanf("%5s", fname);                //read first namae

        while ( (c = getchar()) != '\n' && c != EOF );

        printf("Student's Last Name: "); 
        scanf("%5s", lname);                //read last name
        while ( (c = getchar()) != '\n' && c != EOF );
        printf("Student's Score: "); 
        scanf("%3s", score);                //read score

        while ( (c = getchar()) != '\n' && c != EOF );

        write(sockfd, iEntry, sizeof(iEntry)); //write entry number
        write(sockfd, id, sizeof(id));          //write id
        write(sockfd, fname, sizeof(fname));    //write fname
        write(sockfd, lname, sizeof(lname));    //write lname
        write(sockfd, score, sizeof(score));    //write score
        printf("\n------Student Added------\n");
        i++;

    }
int main()
{
    int sockfd;
    struct sockaddr_in serverAddr;
    socklen_t addr_size;

    sockfd = socket(PF_INET, SOCK_STREAM, 0);
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons(7891);
    serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    memset(serverAddr.sin_zero, '\0', sizeof serverAddr.sin_zero);  

    addr_size = sizeof serverAddr;
    connect(sockfd, (struct sockaddr *) &serverAddr, addr_size);

    func(sockfd);

    close(sockfd); 
}

服务器端:

void func(int sockfd) 
{ 

int i = 0;
char idArr[MAXSIZE][MAXLEN];
char fnameArr[MAXSIZE][MAXLEN];
char lnameArr[MAXSIZE][MAXLEN];
char scoreArr[MAXSIZE][MAXLEN];
char entryArr[MAXSIZE][MAXLEN];
char iEntry[1];

char id[6];
char fname[5];
char lname[5]; 
char score[3]; 
int n,c;
char entry;
// infinite loop for chat 
for (;;) {
    printf("HERE6\n");
    bzero(iEntry, sizeof(iEntry));
    bzero(id, sizeof(id));
    bzero(fname, sizeof(fname));
    bzero(lname, sizeof(lname));
    bzero(score, sizeof(score));
    read(sockfd, iEntry, sizeof(iEntry));
    strcpy(entryArr[0], iEntry);
    if (iEntry[0] == '1')
    {
        read(sockfd, id, sizeof(id));

        read(sockfd, fname, sizeof(fname));
        read(sockfd, lname, sizeof(lname));
        read(sockfd, score, sizeof(score));
        printf("HERE5\n");
        strcpy(idArr[i], id);
        strcpy(fnameArr[i], fname);
        strcpy(lnameArr[i], lname);
        strcpy(scoreArr[i], score);

        printf("Student Added.\n");
        i++;
}
int main()
{
int sockfd, connfd;
struct sockaddr_in serverAddr;
struct sockaddr_storage serverStorage;
socklen_t addr_size;

sockfd = socket(PF_INET, SOCK_STREAM, 0);
serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(7891);
serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
memset(serverAddr.sin_zero, '\0', sizeof serverAddr.sin_zero);  

bind(sockfd, (struct sockaddr *) &serverAddr, sizeof(serverAddr));
if(listen(sockfd,5)==0)
    printf("Listening\n");
else
    printf("Error\n");
addr_size = sizeof serverStorage;
connfd = accept(sockfd, (struct sockaddr *) &serverStorage, &addr_size);

func(connfd); 
close(sockfd); 
}

在我的 func() 函数中，我正在运行一个带有选项的菜单。当使用 PuTTy(即 eros.tx.state.edu)在同一终端上运行时，该程序按预期工作。 当我在两个不同的终端(在同一台机器上)上运行时，程序可以工作，但一旦到达第一个 write() 就退出。

知道为什么会发生这种情况吗？ 很抱歉这篇文章很长，我试图将其保持在最低限度。

Answer 1

char iEntry[1];

好的，iEntry 包含单个字符。

read(sockfd, iEntry, sizeof(iEntry));
strcpy(entryArr[0], iEntry);

为什么要将iEntry传递给strcpy？这是一个单一的角色。您如何期望 strcpy 知道它应该只复制单个字符？

为什么不直接测试iEntry[0]？为什么 iEntry 是一个数组？

您的代码忽略read的返回值。您至少需要通过编写某种“读取全部”函数来精确读取指定的字节数来处理短读取。