RECV缓冲区为空，但返回值> 1

我正在尝试创建一个简单的服务器，以便两个客户端可以相互通信。 主服务器代码接受两个客户端连接，然后分叉使用execl在两个客户端之间生成个人服务器的进程，以便主服务器可以继续查找新连接。 一切似乎工作正常，直到个人服务器试图联系客户，他们都收到胡言乱语，如果有人知道是什么原因导致这一点请告诉我。

接受两个客户端后的主服务器：

if(fork() == 0){ close(listener); int nBytes; char* playerOne[20]; char* playerTwo[20]; //Creates strings to hold file descriptor information for execl char connAscii[sizeof(int)]; char connAscii2[sizeof(int)]; snprintf(connAscii,sizeof(conn), "%d", conn); snprintf(connAscii2,sizeof(conn2), "%d", conn2); fprintf(stderr, "Int conn: %d, asciiConn: %s, backToInt: %d\n", conn, connAscii, atoi(connAscii)); char *argf[2]; argf[0] = connAscii; argf[1] = connAscii2; fprintf(stderr, "that is to say %s and %s\n", argf[0], argf[1]); //Send Handle Request to Connection 1 nBytes = send(conn, handleRequest, sizeof(handleRequest),0); if(nBytes == -1){ perror("send"); exit(1); } //Receive Handle from Connection 1 nBytes = recv(conn, playerOne, 20, 0); if(nBytes == -1){ perror("recv"); exit(1); } //Send Handle Request to Connection 2 nBytes = send(conn2, handleRequest, sizeof(handleRequest),0); if(nBytes == -1){ perror("send"); exit(1); } //Receive Handle from Connection 2 nBytes = recv(conn2, playerTwo, 20, 0); if(nBytes == -1){ perror("recv"); exit(1); } //Send Handle for Connection 2 to Connection 1 nBytes = send(conn, playerTwo, sizeof(playerTwo),0); if(nBytes == -1){ perror("send"); exit(1); } //Send Handle for Connection 1 to Connection 2 nBytes = send(conn2, playerOne, sizeof(playerOne),0); if(nBytes == -1){ perror("send"); exit(1); } //Passes file descriptors to privateServer execl("privateServer","privateServer", connAscii, connAscii2, (char *)0); } 

execl调用的个人服务器：

 char greet[] = {"Hello players, please wait for match setup."}; int main(int argc, char *argv[]) { int conn1 = atoi(argv[1]); int conn2 = atoi(argv[2]); int sent; fprintf(stderr, "Attempting connection with %d\n", conn1); sent = send(conn1, greet,sizeof(greet),0); if(sent == -1){ perror("send"); exit(1); } sent = send(conn2, greet,sizeof(greet),0); if(sent == -1){ perror("send"); exit(1); } fprintf(stderr,"Hopefully they got it\n"); return 0; } 

客户端：通过char读取recv buff char导致乱码并打印整个缓冲区没有显示任何内容，但numbytes == 61。

 char *buff = (char*)malloc(100); memset(&buff[0],0,sizeof(buff)); numbytes = recv(sockfd, buff, 99, 0); //should be from private server if (numbytes == -1) { perror("recv"); exit(1); } buff[numbytes] = '\0'; int i; for(i = 0; i < numbytes; i++){ fprintf(stderr, "%c", buff[i]); } printf("From match server: %.*s (%d bytes)\n", numbytes, buff, numbytes); 

Answer 1

有几个错误：

 char* playerOne[20]; char* playerTwo[20]; 

你想要一个字符数组，而不是一个指向字符的指针数组

改成

 char playerOne[20]; char playerTwo[20]; 

和这里：

 char *buff = (char*)malloc(100); memset(&buff[0],0,sizeof(buff)); 

sizeof(buff)是指向char的指针的大小，更改为

 memset(&buff[0],0,100); 

正如@ user3629249所指出的，不要使用像100这样的幻数

 #define MAX_BUFF 100 char *buff = malloc(MAX_BUFF); memset(&buff[0],0,MAX_BUFF); 

但是如果你使用null终止字符串，则不需要memset 。