我在写两个程序时遇到了一些问题,服务器和客户端。为了保持简单和时间顺序,我首先写了服务器并用telnet和netcat测试了它,并且一切正常(除了read()/ recv()的返回值不同之外,因为它看起来像正常的telnet程序在要发送的字符串末尾添加一个额外的字符,但无论如何...)。c套接字 - 没有收到所有发送的数据
现在我也编写了客户端程序,但是我没有获得其他两个客户端正确接收的所有数据,特别是我从MySQL查询中获得的行[i]字符串。当每次send()函数引入usleet()调用并正确接收所有数据时,情况就会改变。
现在我正在考虑不兼容的缓冲区大小问题(?),但在玩了一段时间并检查了尺寸之后,我无法找到任何东西。
你会发现下面的代码,如果你有任何建议请不要犹豫告诉我。
TNX
/*客户代码*/
#define BUFSIZE 1000
...
void *send_handler(void *);
...
int main(int argc, char *argv[]) {
char buf[BUFSIZE];
...
socket stuff...
...
connect
...
/* receive string from server - working */
bzero(buf, BUFSIZE);
n = read(sockfd, buf, BUFSIZE);
if (n < 0)
error("ERROR reading from socket");
buf[n] = '\0';
printf("%s", buf);
...
/* send username to server - working */
bzero(buf, BUFSIZE);
fgets(buf, BUFSIZE, stdin);
n = write(sockfd, buf, strlen(buf));
if (n < 0)
error("ERROR writing to socket");
...
/* start receiving handler */
if(pthread_create(&thread_id , NULL , send_handler , (void*) &sockfd) < 0) {
perror("could not create thread");
return 1;
}
/* main thread for reading data */
while(1) {
bzero(buf, BUFSIZE);
n = read(sockfd, buf, BUFSIZE);
if (n < 0)
error("ERROR reading from socket");
buf[n] = '\0';
printf("%s", buf);
}
close(sockfd);
return 0;
}
void *send_handler(void *socket_desc) {
//Get the socket descriptor
int sock = *(int*)socket_desc;
char buf[BUFSIZE];
int n;
while (1) {
bzero(buf, BUFSIZE);
fgets(buf, BUFSIZE, stdin);
n = write(sock, buf, strlen(buf));
if (n < 0)
error("ERROR writing to socket");
}
}
/*服务器代码*/
void *connection_handler(void *);
int main(int argc , char *argv[]) {
...
/* socket variables */
...
pthread_t thread_id;
...
socket stuff...
...
while((client_sock = accept(socket_desc, (struct sockaddr *)&client_addr, (socklen_t*)&client_len))) {
if(pthread_create(&thread_id , NULL , connection_handler , (void*) &client_sock) < 0) {
perror("could not create thread");
return 1;
}
}
return 0;
}
void *connection_handler(void *socket_desc) {
//Get the socket descriptor
int sock = *(int*)socket_desc;
...
/* mysql variables */
char cmd[1000];
...
MYSQL_RES *result;
MYSQL_ROW row;
MYSQL *con;
...
/* connection variables */
int read_size, i;
char *message;
char client_message[2000];
char buffer[1000];
...
//clear the buffers
memset(client_message, '\0', 2000);
...
snprintf(cmd, 999, "SELECT field1, field2, field3, field4 FROM files WHERE key='%s' ORDER BY id DESC", var);
if (mysql_query(con, cmd)) {
error checks...
}
result = mysql_store_result(con);
if (result == NULL) {
error checks...
}
else {
num_rows = mysql_num_rows(result);
}
if (num_rows == 0) {
message = "Nothing found\n";
send(sock , message , strlen(message), 0);
}
else {
num_fields = mysql_num_fields(result);
num_rows = mysql_num_rows(result);
snprintf(buffer, 999, "Number of rows: %d\n", num_rows);
send(sock , buffer , sizeof(buffer), 0);
//usleep(10000); // commented, but necessary to work properly...
memset(buffer, '\0', sizeof(buffer));
while ((row = mysql_fetch_row(result))) {
for(i = 0; i < num_fields; i++) {
snprintf(buffer, 999, "%s\t", row[i] ? row[i] : "NULL");
send(sock , buffer , sizeof(buffer), 0);
//usleep(10000);
memset(buffer, '\0', sizeof(buffer));
}
message = "\n";
send(sock , message , strlen(message), 0);
//usleep(10000);
}
message = "\n";
send(sock , message , strlen(message), 0);
//usleep(10000);
mysql_free_result(result);
}
...
}
编辑:我改变 的printf( “%S”,BUF);
与 printf(“Bytes read:%d \ n”,n); 在客户端代码和我获得以下输出:
带有注释usleep()函式:
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 36
Bytes read: 1000
Bytes read: 31
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 2
(17 lines)
与usleep(0)减慢发送流程(获得正确的输出):
Bytes read: 1000
Bytes read: 33
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1
Bytes read: 1
Bytes read: 1000
Bytes read: 31
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1000
Bytes read: 1
Bytes read: 1
(21 lines)
任何提示?
解决:只需用
strlen(buffer);
在服务器部分
更换
sizeof(buffer);
,一切工作正常,即使没有usleep()函式,输出正确/完整。
无论如何。
无法看到你的init套接字,它们是否可以被阻塞? – fghj
而不能看到你如何处理“没有找到”类型的消息,例如你发送没有发现,然后1000字节的结果,在客户端你收到“没有找到”+ 1000 - “找不到”字节,下一次调用阅读返回发送的其余部分。 – fghj
我没有设置任何非阻止选项,所以我假定默认阻止行为。对于什么也没有找到的消息,它工作正常,但也许有1000个字节的错误,因为我嗅探了回环流量,似乎所有的数据都是由服务器发送的(这与telnet一致和netcat输出),但客户端无法全部捕获它 –